Curriculum-based measurement vs mastery measurement

By the IEP Atlas editorial teamLast updated November 1, 2026

Short answer

Curriculum-based measurement gives the same kind of probe all year, each sampling every skill the student should master by the end, so one graph shows overall growth. Mastery measurement tests one skill at a time and moves to the next skill once the student meets the criterion. Ask: does the test change when a skill is mastered? If yes, it is mastery measurement.

Curriculum-based measurement (CBM) and mastery measurement both use short, frequent checks, which is why they get confused. The difference is what each check samples. A CBM probe samples the whole year's target skill on every form, so week 1 and week 30 are the same test in different versions. A mastery measure tests the skill being taught right now, and the test changes when the student masters it.

The IRIS Center describes CBM as a general outcome measure and contrasts it with mastery measurement, which tracks a sequence of short-term skills.^[1] This page puts the two side by side, works through three classroom cases and shows when an IEP needs both. For the monitoring cycle, see the IEP progress monitoring pillar.

The deciding question

Ask one question about the measure: when the student masters a skill, does the test change?

If the test stays the same and the score simply rises, it is curriculum-based measurement.
If the test switches to the next skill, it is mastery measurement.

A grade 3 mixed computation probe that includes addition, subtraction and multiplication on every form is CBM. A sheet of 20 two-digit addition problems, replaced by a subtraction sheet once the student gets 18 of 20 three times, is mastery measurement.

Side-by-side comparison

Feature	Curriculum-based measurement	Mastery measurement
Definition	Brief, standardized probes that each sample the year's whole skill set	Checks on one skill or objective at a time, in a teaching sequence
What changes week to week	Only the form; difficulty stays equal	The skill tested changes after mastery
Graph	One line for the year, rising toward the goal	A series of short lines, one per skill, often in steps
Score	Rate or count, such as words correct per minute or digits correct	Percent correct or items correct on the current skill
Shows retention and generalization	Yes, because older skills stay on every probe	Not by itself; a skill drops off the test once mastered
Sensitivity to daily teaching	Lower; growth shows over weeks	Higher; a new skill shows gains within days
Basis in law or practice	Practice and measurement research; federal law names neither method, but the IEP must say how progress is measured^[3]	Same
Who decides	The IEP team, often using tools the district owns	The IEP team or the teacher, often from the curriculum's unit tests
Example	Grade 4 oral reading fluency passage every week	Reading 20 vowel-team words; move on at 18 of 20 on 3 days
Where it is documented	The goal's measure and the progress report	Short-term objectives or benchmarks, lesson data and the report

How each works on a graph

A CBM graph for a fluency goal has one aimline from the baseline to the year-end goal and one line of weekly points. Every point is comparable, so you can calculate a slope and compare it with the aimline. The guide to rate of improvement calculation shows that math.

A mastery graph looks like a staircase. The student climbs from 6 of 20 to 18 of 20 on short a words, then the next skill starts near zero again. Each step tells you a skill was learned. The whole staircase does not give one slope, and it cannot tell you whether short a words are still solid in March.

The National Center on Intensive Intervention describes progress monitoring as repeated measurement on a consistent tool with a goal line, which is the CBM pattern.^[2] Mastery checks still matter. They tell a teacher what to teach tomorrow.

Three classroom scenarios

Scenario 1: A year-long reading fluency goal

A grade 2 student's goal is to read 70 words correct per minute on grade 2 passages by May. The teacher asks whether to monitor with weekly grade 2 passages or with the decodable books used in lessons.

Answer: CBM, using standardized grade 2 passages. Why: the goal is general reading growth across the year. Lesson books change in difficulty each week, so their scores rise and fall with the book. Score with the oral reading fluency method, and see the reading progress monitoring tools guide for tool types.

Scenario 2: A sequence of multiplication facts

A grade 4 student is learning facts by family, starting with 2s, then 5s, then 10s. The teacher checks each family until the student answers 20 of 20 in 2 minutes, then moves on.

Answer: mastery measurement for teaching decisions, with a mixed CBM probe for the IEP goal. Why: the family checks tell the teacher when to move on. A mixed probe once a week shows whether the 2s stay fluent while the 5s are taught, which is what the annual goal cares about. The guide to math CBM probes covers the mixed probe, and the math facts goal hub has goal wording.

Scenario 3: A task analysis for a daily routine

A student with significant support needs is learning a 10-step handwashing routine. Data are taken on each step, and new steps are taught once earlier steps are independent.

Answer: mastery measurement. Why: there is no general outcome probe for a single routine. The measure is the number of steps done independently, scored with task analysis. Check maintenance by probing the earlier steps after they are mastered.

When you need both

Many IEPs use both, and that is usually the right call. The annual goal is monitored with CBM, which shows overall growth and retention. The short-term objectives or benchmarks are monitored with mastery checks, which show each step in the sequence. Federal rules require short-term objectives or benchmarks only for students who take alternate assessments aligned to alternate achievement standards, though states may require them more broadly.^[3]

A practical setup for a decoding goal:

CBM: a nonsense word probe every week, graphed against an aimline to the annual goal.
Mastery: a 20-word check on the current phonics pattern after each unit, with the criterion written in the objective.

When the two disagree, look closer. Mastery checks passed but a flat CBM line often means the skills are not carrying over to new text. A rising CBM line with failed mastery checks can mean the mastery criterion is too strict or the check is harder than the skill.

Writing the goal so the measure is clear

Name the measure in the goal. "Given a grade 3 mixed computation probe, the student will score 35 digits correct" signals CBM. "The student will solve 2-digit addition problems with regrouping with 90% accuracy on 3 consecutive probes" signals a mastery check, and its criterion defines when it is met. Paste a draft into the goal checker to see whether the measure and criterion are explicit. For how mastery is judged once the data are in, see the guide on IEP mastery criteria.

Frequently asked questions

Is curriculum-based measurement the same as a curriculum test?

No. A curriculum unit test checks what was just taught and changes each unit. A CBM probe samples the whole year's skill on every form and stays equal in difficulty, so scores can be compared across the year.

Which is better for an IEP goal?

For a year-long goal on a broad skill such as reading fluency or computation, CBM usually gives a clearer graph. For a teaching sequence or a routine, mastery measurement fits. Many IEPs use CBM for the goal and mastery checks for the objectives.

Can mastery measurement show whether a student keeps a skill?

Not by itself, because a mastered skill drops off the test. Add maintenance probes on earlier skills, or pair the mastery checks with a CBM probe that keeps every skill on each form.

Use it in IEP Atlas

Sources

Classroom Assessment (Part 1): An Introduction to Monitoring Academic Achievement in the Classroom, IRIS Center, Vanderbilt University
Progress Monitoring: Data & Goal Setting, National Center on Intensive Intervention
34 CFR §300.320: Definition of individualized education program, Legal Information Institute, Cornell Law School

Written and checked by the IEP Atlas editorial team under our editorial policy. This guide describes general practice and federal rules. It is not legal advice; your state may add requirements, and the IEP team makes the decisions for each student.