Interleaved practice in math: what it is, how to set it up, and what the research says
Mixing different kinds of problems in one practice set, so students have to work out which method each problem needs, instead of practicing one kind in a block.
What the research says
- Strong
- Promising
- Mixed
- Thin
- Contradicted
Promising for math, with an unusually strong recent trial. In a pre-registered randomized trial with 54 seventh-grade math classes, students who did interleaved assignments outscored those with blocked assignments on an unannounced test a month later (61% versus 38%), and teachers ran it without training. A meta-analysis of 59 studies found a small benefit for math tasks and a moderate one overall, but not for every kind of material: for learning words, blocking was better. Mix problem types that students must learn to tell apart.
Rated Promising. One synthesis, one school trial and one lab or classroom experiment support it. One review or weaker study adds context but doesn't move the rating. How we rate the evidence
Checked against each source in October 2026.
The studies behind this rating
Seventh-grade classes that periodically did interleaved assignments for four months outscored classes that did blocked assignments on an unannounced test a month later. Teachers carried it out without training and supported it in an anonymous survey taken before they knew the results.
Sample 54 seventh-grade math classes, cluster randomized, pre-registeredWho School-age childrenEffect 61% vs 38% on an unannounced test a month later, d = 0.83Read it at the source (opens in a new tab)For math tasks, interleaving had a small benefit (g = 0.34), and a moderate one overall (g = 0.42). It worked best when categories were similar to each other; for learning words, blocking did better (g = -0.39), and for expository texts results were unclear.
Sample 59 studies, 238 effect sizes in 158 samplesEffect overall g = 0.42; mathematical tasks g = 0.34; paintings g = 0.67; words g = -0.39 (blocking better)Read it at the source (opens in a new tab)Seventh graders who practiced with problems of different kinds mixed together (interleaved) scored higher on unannounced tests one day and thirty days later than when the same problems came in blocks of one kind, and the advantage was larger after a month.
Sample 126 seventh graders, the same practice problems over three monthsWho School-age childrenEffect Cohen's d = 0.42 on a test one day later; d = 0.79 thirty days laterRead it at the source (opens in a new tab)Rated interleaved practice moderate utility: promising, but the benefits had only begun to be explored systematically in 2013.
Sample Ten study techniques, each reviewed across learners of different ages, materials and testsWho School and collegeRead it at the source (opens in a new tab)
What it is
Most math practice is blocked: after a lesson on the area of triangles, students do twenty triangle problems. They know which method to use before they read each problem, because it's always the one from today's lesson.
Interleaved practice mixes the problem types. A set might include a triangle area problem, then a circle, then a rectangle, then a word problem that needs one of those, in an order where no two neighbors need the same method. Students have to look at each problem and decide what kind it is, which is exactly what they'll have to do on a test or in the next course.
Doug Rohrer and colleagues describe the difference this way: in blocked practice the strategy is chosen for the student by the assignment; in interleaved practice the student must choose it from the problem itself.
Interleaving often comes together with spacing, because mixing in older problem types means coming back to them over weeks. But the two are different. Spacing is about when you practice the same thing; interleaving is about what's next to what in a session. Our spaced practice card covers the first.
Why it works
Knowing how to do a procedure isn't enough; students also have to know when to use it. Blocked practice trains the how and skips the when. Interleaving makes students compare problems and notice the features that tell them apart, which is the skill that falls apart on a mixed test.
The strongest evidence is Rohrer and colleagues' 2020 randomized trial. Fifty-four seventh-grade math classes were randomly assigned to periodically do interleaved or blocked assignments over four months; both groups then did the same interleaved review. A month later, on an unannounced test, the interleaved classes scored 61% and the blocked classes 38%. Teachers carried it out without training, and in an anonymous survey taken before they knew the results, they supported it.
An earlier classroom experiment by the same team, with 126 seventh graders working the same problems for three months, found interleaved practice beat blocked practice on tests one day and thirty days later, with a bigger advantage after a month.
Matthias Brunmair and Tobias Richter's meta-analysis of 59 studies puts this in context. Interleaving had a moderate benefit overall and a small one for math tasks, and worked best for visual material such as paintings. It helped most when the categories being learned were similar to each other (which is when students most need to tell them apart). For learning words, blocking was better, and for expository texts the results were unclear.
How to start, by grade
Grades 3–5
- Teach a new skill with blocked practice first, so students can do it at all.
- From the next week, make part of each practice set interleaved: mix the new problem type with two or three earlier ones that look similar.
- Mix word problems that need different operations, so students must decide whether to add, subtract, multiply or divide.
- Ask students to label each problem with its type before solving it, at least at first.
- Use the math worksheet generator to make mixed sets quickly.
Grades 6–8
- Rearrange existing homework: keep the same problems, but split each set so a third to a half are from earlier lessons, in mixed order.
- Interleave problem types students confuse: area and perimeter, the area formulas for different shapes, proportional and non-proportional relationships, types of equations.
- Make sure no two neighboring problems need the same method.
- Before a unit test, give an interleaved review rather than a review of each lesson in order.
- Students may find mixed sets harder, because they have to choose the method; explain that choosing is the skill being practiced.
Grades 9–12
- Build cumulative, interleaved problem sets for each unit that include earlier units' problem types.
- Use interleaved quizzes before exams so students practice choosing methods, not just carrying them out.
- Keep blocked practice for the first encounter with a new technique, then switch to mixed sets.
Examples
Area formulas, mixedGrades 5–7
After teaching areas of rectangles, triangles and parallelograms in separate lessons, a practice set mixes them: a parallelogram, then a triangle, then a rectangle, then a composite shape. Students first write which formula each needs, then solve. Mistakes now show who can't yet tell a triangle's height from a parallelogram's side.
Which operation?Grades 3–5
A set of eight word problems, two each needing addition, subtraction, multiplication and division, in shuffled order. Before solving, students circle the operation and say why. Blocked sets let students skip that step; this set makes it the point.
Rearranged homeworkGrades 6–8
A teacher keeps the textbook's problems but rearranges them: each night's ten problems include five from today's lesson and five from the previous three weeks, mixed. Over a unit, students meet each type many times, in no predictable order.
Interleaved test reviewGrades 6–12
Instead of reviewing a unit lesson by lesson, the review sheet mixes every type of problem from the unit at random. Students work in pairs, and for each problem first agree on what kind it is. The test will be mixed; now the practice is too.
Common mistakes
- Interleaving before students can do each skill.
- Students need to know a method before they can choose between methods. Teach new skills with some blocked practice first, then interleave.
- Mixing unrelated problem types.
- The benefit comes from telling similar things apart. Brunmair and Richter found larger effects when categories were similar. Mix problems students might confuse, not random topics.
- Interleaving vocabulary lists.
- For learning words, blocking did better in the meta-analysis. Use interleaving mainly for problem types and categories to be told apart.
- Judging it by practice scores.
- Interleaved practice can feel harder at the time, because students must choose the method for each problem. Judge it by tests later, where the trials found the advantage.
- Abandoning it because students complain.
- Explain why it's harder, show them their results on later tests, and keep the practice itself low-stakes and ungraded.
Time and cost
Time: none extra. The same problems, in a different order.
Money: nothing.
Training: very little. Teachers in the 2020 trial implemented it without training. The main work is rearranging practice sets, which a worksheet generator or a shared problem bank makes quick.
Debates and open questions
How general is it? The best classroom evidence is in middle school math. The meta-analysis shows the effect depends on the material: helpful for math and visual categories, unclear for expository texts, and reversed for words. We'd be cautious about interleaving outside problem types and categories.
Is it really interleaving, or spacing? Interleaved assignments also space practice of each problem type over time, so classroom studies can't fully separate the two. For teachers, the combination is what matters, and both point the same way.
Why only Promising? Our rule needs two syntheses, or one synthesis and two school trials, for Strong. Interleaving has one synthesis, one large school trial and a smaller classroom experiment. Another large trial would likely move it up.
Tools that do it
Free, on this site, nothing to sign up for. Class lists stay in your browser.
- Math worksheet generator: make practice sets that mix several problem types in shuffled order.
- Math worksheets by topic and grade: pull problems from several topics into one mixed set.
- Review game board maker: a review game with categories from different units, so teams meet mixed problem types.
- Flashcard maker: shuffle cards from several topics together rather than studying one deck at a time.
Questions teachers ask
- What's the difference between interleaving and spacing?
- Spacing spreads practice of the same skill over time. Interleaving mixes different skills within one session so neighbors need different methods. Mixed review usually does both, but the research treats them separately.
- Does interleaving work outside math?
- Brunmair and Richter found it helped with visual categories such as paintings and was unclear for expository texts, and that blocking was better for learning words. It's most useful wherever students must tell similar types apart.
- How much of each assignment should be interleaved?
- A common approach is to keep some practice on the newest skill and make the rest mixed from earlier lessons. The 2020 trial periodically replaced blocked assignments with interleaved ones over four months.
- Do I need a new textbook or program?
- No. The 2020 trial rearranged practice problems into a different order; teachers carried it out without training. You can interleave the problems you already have by mixing earlier problem types into each assignment.
- Will my students' grades drop?
- Practice scores may dip, because interleaved problems ask more of students. Keep practice low-stakes; the advantage shows up on later tests, which is what the trials measured.
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Cite this card
Written for teachers by Peabody Teach from the sources listed above, which we read on the publisher's or clearinghouse's own page. We summarize and link; we don't copy. No ads, no affiliate links. Something wrong or out of date? Tell us.