Intervention Session Frequency and Duration: Four Meanings
You have a student for fifty minutes on a Tuesday. The program manual on your shelf was written for forty-five minutes a day, five days a week. Somewhere between those two facts sits a decision you make every week and almost never write down.
Intervention session frequency and duration are the two numbers most often quoted and least often defined. A publisher states them as a schedule. A research panel states them as a range. A certifying body states them as a practicum condition. And the framework the field cites most for intervention intensity defines dosage as something else entirely, in two of its own documents, differently.
This is not a piece about whether once-weekly work helps. That question is not settled by the published record in either direction, and nothing here should be read as answering it. This is a piece about what the specifications actually say, who issued them, and what you can honestly claim when your schedule and the manual disagree.
It is written for practitioners who carry a caseload rather than a timetable: educational therapists, learning specialists and executive function coaches, whose distinct scopes share this one constraint. If you want the scope question rather than the schedule question, the practitioner scope map is the piece to read first.
Dosage has two definitions, and NCII published both
The National Center on Intensive Intervention maintains the Taxonomy of Intervention Intensity, the seven-dimension framework most commonly cited when practitioners talk about intensity. It is built on Fuchs, Fuchs and Malone, published in Teaching Exceptional Children and indexed at ERIC EJ1160167; an author manuscript is openly available.
On NCII's Taxonomy page, dosage is defined this way, verbatim:
Dosage: the number of opportunities the student has to respond and receive feedback from the teacher
No minutes. No sessions. No group size. Dosage is a count of responses.
On NCII's own Taxonomy overview handout, the same dimension reads:
The number of opportunities a student has to respond and receive corrective feedback. It refers to the size of the instructional group, the number of minutes each session lasts, and the number of sessions provided per week.
The second sentence is doing enormous work. It converts an unobservable quantity into three observable proxies, and those proxies are what everyone then reports. Both documents were live on 17 September 2026, and this article was checked against both on that date.
The distinction matters in a very practical way. If dosage is opportunities to respond, then a fifty-minute one-to-one session and a fifty-minute session in a group of six are not the same dose, and the schedule alone will never tell you which you delivered. If dosage is minutes times sessions per week, they are identical.
The same handout is unusually direct about a second dimension. Strength is defined as how well the program works for students with intensive needs, expressed in effect sizes, with thresholds stated plainly: above 0.25 indicates value, 0.35 to 0.40 is moderate, and 0.50 or larger is strong and preferred. That is a rare published number in a field that mostly publishes adjectives.
What the publishers actually specify
Reading publishers are the most forthcoming group in the whole intervention market on this question, which is why they are the useful place to start. Every figure below was read from the publisher's own page on 17 September 2026.
Wilson Reading System
The program page states that one full lesson consists of all three Blocks of instruction, at "approximately 30 minutes to complete each Block," and requires a "minimum of two complete lessons per week." Grouping is "Small group (ideally up to four students), one-to-one." Delivery is restricted to a Level I certified Wilson Dyslexia Practitioner or a Level II certified Wilson Dyslexia Therapist.
Read that as a weekly figure and it is roughly three hours, delivered across at least two contacts, by a certified practitioner. Wilson publishes no total program duration, and this article does not assert one.
Take Flight
Scottish Rite for Children publishes the most complete specification in the field. Take Flight "includes 132 new learning days and 98 application days for a total of 230 days of direct instruction." It is "designed for small group instruction (two to six students) for a minimum of 45 minutes per day, five days each week."
There is one published alternative, and it is a rearrangement rather than a reduction: "Alternatively, the lessons can be taught for 60 minutes each day for four days a week." Both routes deliver 240 minutes a week. The program is described as designed for use by dyslexia therapists with children aged seven and older.
Barton Reading and Spelling System
Barton is the only program in this group that publishes a weekly floor and a session ceiling in the same document. Its FAQ states: "You must provide at least 2 hours of one-on-one tutoring each and every week." And separately: "A tutoring session should never last more than an hour."
Those two sentences together are a requirement for at least two sessions a week, stated without ever using the word frequency.
Barton also publishes a completion estimate almost nobody else does. At two one-hour sessions a week, a student with "classic, or moderate, dyslexia" takes "from 2 to 3 years to complete the entire Barton System," and "It takes most students 3 to 5 months to complete a level once they reach Level 3." The maximum group size is three-on-one.
LiPS
The Lindamood Phoneme Sequencing program's fact sheet, published by Lindamood-Bell and distributed through Gander Publishing, states 80 to 120 lessons across PreK to grade 12. Session length is given by tier: 30 to 45 minutes for Tier 2 in groups of five to eight, and 60 to 120 minutes for Tier 3 in groups of five or fewer.
The fact sheet then adds a sentence worth quoting on its own: "Lesson times are minimums. Some students may require more intensive intervention." Weekly frequency is not stated anywhere in the document.
The programs whose published figures have moved
Two entries in this survey did not re-confirm, and saying so is more useful than quietly repeating what was recorded earlier.
This site published in August 2026 that S.P.I.R.E. specifies "45+ Minutes Per Session" and that Corrective Reading specifies 35 to 45 minutes of teacher-directed work delivered daily.
Both figures were read from the publishers' pages at the time. On 17 September 2026 neither figure appears on the current pages. The S.P.I.R.E. overview has been rebuilt around a fourth edition and carries no session length in the page as served; McGraw Hill's Corrective Reading page states no session length or frequency of its own, offering only a customer testimonial describing 45 minutes four days a week.
That is a finding about the published record, not an accusation about either publisher. Product pages are rebuilt, specifications move to manuals and sample lessons, and a figure that was on a page last month may be in a scope-and-sequence document this month. The practical instruction is narrow: before you cite a dose in a report or a parent letter, open the publisher's current page, and record the date you read it.
What the research documents specify, and what they do not
If publishers are the most forthcoming source of dosage figures, the federal evidence documents are the least, and the gap between them is the single most surprising thing in this area.
The 2009 reading guide gives numbers
The What Works Clearinghouse practice guide Assisting Students Struggling with Reading carries the clearest dosage statement in the federal literature. Its Recommendation 3, rated at the strong evidence level, calls for intensive systematic instruction on up to three foundational skills in small groups, with those groups typically meeting "between three and five times a week, for 20 to 40 minutes."
Its Recommendation 5, covering students who have made minimal progress in Tier 2, calls for intensive instruction "on a daily basis." That recommendation sits at the lowest evidence tier the guide uses, labelled "low" in the original 2009 document and displayed as minimal on the current WWC site. Quote the recommendation and quote its tier in the same breath.
The 2022 guide for grades 4 to 9 gives none
Providing Reading Interventions for Students in Grades 4-9 (WWC 2022007, March 2022, also at ERIC ED617876 and as a summary PDF) is the most current federal guidance for the age band most educational therapists work with. Its four recommendations concern decoding multisyllabic words, purposeful fluency-building, comprehension-building practices, and practice with challenging text, rated Strong, Strong, Strong and Moderate.
On dosage it says essentially nothing. A direct read of the guide on 17 September 2026 located no recommended number of minutes per session and no recommended number of sessions per week. On group size it offers only a descriptive observation in the introduction, that group size "typically varies, with smaller groups in grades 4 and 5 than in elective reading courses in middle and high schools."
So the strongest current evidence document for adolescent reading intervention makes four strongly-rated recommendations about what to teach and declines to specify how long or how often. That is worth holding onto.
It means a practitioner who cannot match a publisher's schedule has not departed from an IES recommendation. There is no IES recommendation to depart from. The guide was produced for IES by Mathematica, whose project page carries the same four recommendations and the same silence on dose.
The pattern repeats across the other guides in this family. The math guide Assisting Students Struggling with Mathematics (WWC 2021006, March 2021) recommends practices, not schedules. Improving Adolescent Literacy (NCEE 2008-4027) does the same, and its recommendations concern classroom instruction rather than one-to-one work, which is a boundary worth stating when quoting it.
What the intensification literature says
The IRIS Center's Intensive Intervention Part 1 module devotes a page to changing dosage and time, and it is the most concrete practitioner-facing treatment available.
It separates three things that are usually collapsed: frequency of intervention, length of instructional sessions, and duration of the intervention. Its worked examples are increasing weekly meetings "from two sessions to four sessions," increasing session length "from 30 minutes per session to 45 minutes per session," and increasing the run "from 10 to 20" weeks.
The page then reports research ranges for elementary students: "Duration of intervention: at least 8-16 weeks" and "Length and frequency of intervention: 30-120 minutes per day," with a note that secondary students who struggle with reading might need more time. Those ranges are attributed on IRIS's references page to Vaughn and colleagues, and they are ranges drawn from school-based research, not a rule issued by IRIS.
The same page carries the caution that matters most here, and it cuts against a purely arithmetic reading of dosage. Under its research note it reports that students with severe and persistent learning challenges "might require ten to thirty times more opportunities to practice than their peers to effectively apply the skill or strategy," attributing this to the Gersten-led panel behind the 2009 guide. Opportunities, again, not minutes.
And it says plainly that added time is not self-justifying: the guidance is to keep the student actively engaged, limit nonproductive time, teach additional skills and concepts, provide more practice with corrective feedback, and teach step by step.
The one federal recommendation that is about time is rated Minimal
There is a further wrinkle in the federal guidance that is easy to miss and hard to unsee once noticed.
The WWC practice guide Teaching Elementary School Students to Be Effective Writers (NCEE 2012-4058, June 2012, revised October 2018, also at ERIC ED533112) makes four recommendations. Recommendation 1 is "Provide daily time for students to write." It is rated at the guide's minimal evidence level.
Recommendation 2, on teaching the writing process, is rated Strong. Recommendation 3, on handwriting, spelling, sentence construction and typing fluency, is rated Moderate and rests on nine studies, seven of which involved populations the panel determined were at risk for writing difficulties.
So in the one guide where a panel made an explicit recommendation about how much time, the time recommendation drew the weakest rating in the document and the instructional-content recommendations drew the strongest. Report that as a fact about the guide's ratings, not as evidence that time does not matter.
What the tutoring literature specifies
The National Student Support Accelerator at Stanford defines high-impact tutoring as "intensive, relationship-based, and individualized instruction that leads to substantial learning gains for students by supplementing, but not replacing, students' classroom experiences." Among its stated characteristics are "Regular sessions (3+ times per week for 10+ weeks)" and "Small-group formats (one-to-one is optimal; no greater than one-to-four)."
That is a definitional threshold rather than a program specification, and the distinction is worth keeping. It tells you what a body of research was studying when it reported gains. It does not tell you what happens below the threshold, because programs below the threshold were largely not what was studied.
The arithmetic nobody publishes
Put the published specifications next to a real private-practice schedule and the gap is not subtle. The figures below are arithmetic performed on the quoted specifications above, not claims by any publisher.
Take Flight, as specified: 45 minutes a day, five days a week, 230 days of direct instruction. That is 172.5 hours of instruction, and at five days a week it spans roughly two school years.
Wilson, as specified: two complete lessons a week, each approximately 90 minutes across three Blocks. That is about three hours a week.
Barton, as specified: at least two hours a week, in sessions no longer than an hour, for two to three years for a student with moderate dyslexia.
LiPS at Tier 3, as specified: 60 to 120 minutes per session across 80 to 120 lessons, with those session times described as minimums.
A once-weekly private practice hour across a 36-week school year: 36 hours.
Nobody should read that list as a verdict. What it is, precisely, is the reason the conversation at intake is hard.
A single weekly hour across a full school year delivers roughly a fifth of the instructional time Take Flight specifies. Those are ratios between published figures. They are not predictions about any student.
The gap between a published specification and a private caseload is not a secret and not a scandal. It is simply undocumented, and documenting it is work a practitioner can do in one paragraph.
There is a second arithmetic point that is easier to miss. If dosage is opportunities to respond, then group size sits inside the number. A 50-minute session with one student and a 50-minute session with four students are the same minutes and, on NCII's own primary definition, not the same dose.
For a private practitioner working one-to-one, that arithmetic runs in your favour, and it is the one dimension where a small practice is structurally advantaged over a school-based group.
The dosage gap is not the same in every subject
The reading programs above are the field's best-disclosed corner. Move one subject sideways and the published record thins fast, which means the question "what dose does this program specify?" often has no answer at all.
Math
Across the eight commercial math intervention programs surveyed for this site's map of math intervention for dyscalculia, exactly one publishes a lesson count and a lesson length together.
Do The Math, from Heinemann, states that each module is "30 half-hour lessons," across four addition and subtraction modules, three for multiplication, three for division and three for fractions, for grades 1 to 5, with a separate middle school version. Group size is not stated.
Everyone else publishes levels, strands, grade bands and features. Corrective Mathematics publishes seven modules and a grade range and no session length. TouchMath publishes a program description and no dosage at all.
Where a real math dosage figure exists, it usually comes from the research rather than the vendor. NCII's Number Rockets taxonomy brief states that "Tutors deliver the program to small groups of two to four students three times per week in 40-minute sessions, with 30 minutes of mathematics instruction and activities followed by 10 minutes of practice." That is a study parameter, described as such.
Writing
Writing sits with math rather than with reading, as this site's survey of writing intervention tools found. Handwriting curricula mostly publish a sequence and no dose.
Expressive Writing publishes 39 lessons in Level 1 and no lesson length. The Writing Revolution declines the question on principle, stating that the Hochman Method "is not a separate writing curriculum but rather an approach designed to be adapted to and embedded in the content being taught."
The most completely specified writing intervention located for that survey is published by a third party rather than by its developer.
The Fundamentals in the Sentence Writing Strategy, from the University of Kansas Strategic Instruction Model, is listed on NCII's academic intervention tools chart with a full set: grades 2 to 12, individual or small groups of four to six, a minimum of 25 minutes per session, at least five sessions weekly, a minimum of six weeks, continuing until mastery of all 27 lessons, delivered after three to six hours of training.
Those figures were read from the chart entry on 10 September 2026 and could not be re-read on 17 September 2026, because the tools chart renders its entries through JavaScript and serves an automated fetcher a page with no tool data in it. If the numbers are load-bearing for a decision you are making, open the chart in a browser and read the entry yourself.
Executive function and coaching
Here the record is thinnest of all. This site's comparison of executive function curricula found four different kinds of object wearing one label, and the manualised trial protocols in that group carry dosage figures only because they were trials. The practitioner frameworks in the same group are not programs and specify nothing, correctly.
For coaching there is no published dose at all. Nothing in the credentialing landscape mapped in how to become an executive function coach specifies a session frequency or duration for practice, as distinct from for training. A practitioner working on executive function has no published specification to fall short of, which is a different problem rather than a smaller one: there is nothing to check fidelity against.
A specification is a specification, and departing from it is a fidelity question
The published record supports a narrow set of claims about what happens when delivery does not match the specification, and it is worth being exact about them.
A publisher's stated schedule is the condition under which the publisher describes its program as being implemented. Where that program carries an efficacy claim, the studies behind the claim were run at or near those parameters. So a delivery schedule below the specification is, in the first instance, a fidelity question rather than an outcomes question, and the publisher's own implementation documentation is the authority on it.
What the record does not support is an inference in either direction about results. No study was located for this article examining these specific programs delivered at a reduced weekly dose in private practice, and no publisher in this survey publishes a minimum below which it considers its program no longer itself.
Both absences should be reported as absences. The honest position is that a reduced schedule is a documented departure from a published specification whose consequences for that program are not established in the public record.
A schedule below the manual is a fidelity fact. It is not, on this evidence, an outcome prediction, and the field has no basis for treating it as one in either direction.
What you can do is describe it accurately. If you are drawing on a program's materials at a schedule the publisher does not specify, say that in the treatment plan rather than naming the program as though it were being implemented as published. This site's guidance on writing an educational therapy treatment plan treats that kind of precision as the plan's main job, and this is the clearest case for it.
The ethics anchor is ordinary rather than dramatic. AET's Code of Ethics governs how you represent your services, and describing a weekly session as delivery of a program specified at five sessions a week is a representation question before it is anything else.
When several organisations share a vocabulary
This is the eighth time a piece on this site has found one word carrying several incompatible meanings, and the pattern has become the most reliable thing to check first in any new area.
The comparison of reading intervention programs found that these programs are not the same kind of object, so a head-to-head table is a category error. The piece on what "Orton-Gillingham based" actually means found that no organisation adjudicates the claim at all.
The map of math intervention for dyscalculia found the field's dominant vocabulary missing from the strongest evidence document in the area, and it named the dosage gap directly: exactly one of eight commercial math programs publishes a lesson count and a lesson length together.
The survey of dysgraphia and writing intervention tools found two authoritative bodies defining one word as two different disorders, and found writing publishers sitting with math rather than with reading on dosage disclosure. The comparison of executive function curricula found four kinds of object wearing one label. The piece on achievement test qualification levels found that a letter is a purchasing rule for one storefront rather than an industry scale.
And the article on educational therapy supervision requirements found six bodies counting supervised practice in six different units, which is where this piece started. Dosage is the same finding applied to the clock.
The credentialing bodies specify a dose too, and you may never repeat it
There is a quiet irony in the certification landscape that practitioners notice and rarely name.
CERI's Structured Literacy Dyslexia Interventionist practicum is specified as one student, two academic semesters of twelve consecutive weeks each, 24 sessions per semester, delivered "2x/week for 60 minutes non-consecutive days or 3x/week for 45 minutes," with three formal lesson observations. The Specialist level applies the same session figures to each of three heterogeneous students.
Wilson's Level I certification requires a minimum of 65 lessons with a written lesson plan for each and five observations of roughly 60 to 75 minutes. ALTA's CALT application requires a minimum of 700 clinical and teaching practicum hours with a minimum of ten demonstrations.
The Orton-Gillingham Academy's Associate level requires 100 hours of supervised practicum over eight consecutive months, with ten observed lessons of 40 to 60 minutes; its Certified level compounds that to 300 hours across two academic years.
So the credential you hold was very likely earned at a frequency your current caseload cannot sustain. That is not a contradiction and nobody is being inconsistent.
A practicum is designed to demonstrate competence under favourable conditions; a caseload is designed around families, school schedules and what people can pay for. But it does mean the dose in your training file and the dose in your appointment book were never the same number, and the field has never written down what to do about that.
And one accreditor counts a group hour as a single session
IMSLEC's accreditation level standards, re-read on 17 September 2026, set a published exchange rate that nobody else in this area publishes. At Therapy Level the practicum requirement is stated as "700 — 500 — 350" hours against "10 — 15 — 20" direct observations, over a 24-month minimum, with 200 total course contact hours and a master's degree. More observation buys fewer hours, explicitly and on a stated scale.
Beneath each level's table sits a single-sentence footnote, repeated at every level, verbatim: "Group instruction counts as one session."
Set that beside NCII's definitions and you have the cleanest collision in this whole article. For NCII, group size sits inside dosage; teaching four students for an hour is not the same dose as teaching one.
For IMSLEC's practicum accounting, teaching a group is one session, full stop. Neither body is wrong. They are counting different things for different purposes, and the word "hours" is doing the disguising. This site's article on what supervised hours actually mean found the same disguise operating across six bodies.
AET's own accounting runs a third way again. Its ET/P membership page requires documentation of 1,500 direct service hours, defines direct service as "the time spent with an individual student or client," and excludes preparation and report writing by name. That is an hours count with no frequency attached at all.
What you can change when you cannot change the dose
The most useful feature of the Taxonomy is that dosage is one dimension of seven, and the other six are largely free of the calendar.
NCII's implementation page lists them verbatim. Strength, the evidence of effectiveness for students with intensive needs. Dosage. Alignment, how well the intervention matches the targeted skills and grade-appropriate standards.
Then: Attention to transfer, whether the intervention is explicitly designed to help students connect skills across contexts; Comprehensiveness, how well it incorporates explicit instruction principles; Behavioral or academic support; and Individualization, the ongoing use of progress monitoring and diagnostic data to adapt the intervention.
Read that list as a practitioner with one hour a week and several of the dimensions are things a small practice does better than a school, not worse.
Alignment is a caseload-of-one advantage. The handout defines it as addressing the student's full set of skill deficits while not addressing skills already mastered. A group program cannot skip what one student has mastered. You can.
Individualization is the dimension the whole data-based individualization process exists to serve, and NCII is explicit that DBI "is a process, not a specific program or product." Its decision rules are usable at any frequency.
Attention to transfer is largely a design choice about what you ask the student to do between sessions, and a weekly schedule makes the between-session interval the main event rather than an afterthought.
Comprehensiveness is about explicit instruction principles, which are properties of how you teach rather than how often.
None of this is a substitute for time and it should not be sold as one. It is the difference between a practitioner who has thought about intensity along seven dimensions and one who has thought about it along one.
The IRIS caution applies in reverse as well. If more minutes are not automatically more dose, then fewer minutes are not automatically less dose either. The number of opportunities to respond in a tightly-run one-to-one hour is a real quantity, and it is one of the few things in this area you can actually count for yourself.
What to do at intake
A short sequence, in order, and it is a sequence rather than a decision.
Find the publisher's current page for whatever program or materials you are drawing on, and read the stated schedule today rather than from memory or from a training binder.
Write down what you can actually offer: minutes, sessions per week, weeks per year, group size.
Name the gap in writing, to yourself first and then to the family, in figures rather than adjectives.
Decide explicitly whether you are implementing the program or drawing on its materials, and use the language that matches.
Choose which of the other six Taxonomy dimensions you are going to work hardest, and record that choice in the plan.
Set your progress monitoring so the plan is answerable by data rather than by argument, which is what NCII's decision rules are for.
None of those steps requires you to promise an outcome, and step four is the one that protects you.
Two free templates do most of the paperwork. NCII publishes an intervention plan template built for individual students or small groups, and a set of academic intervention taxonomy briefs that score programs on the tools chart across all seven dimensions, which is a faster way to see where a program is strong than reading its marketing.
For the assessment side of the same conversation, IDA's Knowledge and Practice Standards for Teachers of Reading, second edition 2018, sets out at Standard 3.5 the expectation that a practitioner can conduct progress monitoring with curriculum-based measures, graphing included. A plan whose dose is below specification and whose monitoring is sound is a defensible plan. One with neither is not.
Where the published record runs out
Several things a practitioner would reasonably want to know are simply not in the public record, and this article did not fill them in.
No publisher in this survey states a minimum weekly dose below which it considers its program no longer being implemented. Wilson states a minimum of two lessons a week and Barton states a minimum of two hours a week; neither says what a single weekly session constitutes.
No study was located examining these specific programs delivered at reduced frequency in private practice. The absence is an absence in the searched record, not evidence that reduced frequency is equivalent or inferior.
S.P.I.R.E.'s and Corrective Reading's session parameters could not be re-confirmed from the publishers' current pages on 17 September 2026. Figures in circulation may be accurate and drawn from manuals not published online. Treat any figure you cannot source to a current publisher document as unsourced.
IES's current guide for grades 4 to 9 recommends no dose at all. Any minutes-per-week figure attributed to it is an attribution error.
NCII's two published definitions of dosage differ in scope. Where a dosage figure is quoted to you, ask which definition it was built on.
Group size is inside the dosage definition on both NCII documents, and almost nobody reports it alongside minutes. A dose reported without a group size is incomplete on its own source's terms.
Not everything useful is a program with a dose to publish. Self-Regulated Strategy Development is a six-step instructional procedure rather than a product, and CERI's Structured Literacy Classroom Teacher certificate carries no practicum at all and says in terms that its holders "do not provide specialized, remedial reading interventions to students." Neither absence is a defect.
NCII's own tools chart user guide states that the charts are "not intended to endorse any program or tool, or to compare programs or tools to one another." A dosage figure lifted from a chart entry is a description of what was studied, not a recommendation.
That list is the honest boundary of what can be said today. Where a number here is load-bearing for a decision you are about to make, open the source, read it yourself, and record the date.
Frequently asked questions
Is there a recommended number of intervention minutes per week?
Not as a single figure, and it depends entirely on which document you are reading. The 2009 WWC reading guide describes Tier 2 groups typically meeting three to five times a week for 20 to 40 minutes, at its strong evidence level.
IRIS reports research ranges of 30 to 120 minutes per day over at least 8 to 16 weeks for elementary students. The 2022 WWC guide for grades 4 to 9 recommends no schedule at all. Cite the document, the figure and its evidence tier together, never the figure alone.
Does a weekly session count as implementing a program like Wilson or Take Flight?
Those publishers specify otherwise. Wilson states a minimum of two complete lessons per week and Take Flight specifies 45 minutes a day, five days a week. Neither states what a lesser schedule constitutes, so the accurate description is that you are drawing on the program's materials rather than implementing it as published. That distinction is a representation question, and it belongs in the treatment plan.
What is the difference between dosage and intensity?
Dosage is one of the seven dimensions of intensity in NCII's Taxonomy, alongside Strength, Alignment, Attention to transfer, Comprehensiveness, Behavioral or academic support, and Individualization. Intensity is the whole set. A practice that cannot increase dosage can still increase intensity along the other six, and the Taxonomy exists partly to make that visible.
Does group size change the dose?
On NCII's own definitions, yes. The Taxonomy overview handout names the size of the instructional group as one of the three things dosage refers to, and the primary definition on NCII's Taxonomy page is opportunities to respond, which group size directly constrains. A one-to-one hour and a group hour are the same minutes and are not the same dose.
Where do the dosage figures quoted in the field come from?
Three different places, and they are routinely mixed. Some come from publishers, who state them as implementation conditions. Some come from research panels, who state them as ranges observed in studies. Some come from the study parameters of a single trial and are then repeated as if they were a specification. When a figure has no source attached, the most likely explanation is the third.
If I cannot deliver the specified dose, what should I change first?
Alignment, on the framework's own logic, because it is the dimension a one-to-one caseload can move furthest at no cost in time: teach the student's actual skill gaps and stop teaching what they have mastered.
Then individualization, which is what progress monitoring and NCII's decision rules are for. Then document the gap between your schedule and the published specification, because an undocumented departure is the only version of this that creates a problem.
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