The studies
Reviewed · 1 min read
Every grade on this site rests on the studies in this table. Each row says what kind of study it was, who was studied, what it was compared with, what it found, and where it falls short. Filter by grade band, subject, design or principle.
How to read the design column, and why a correlation never earns a grade, is explained on How we grade the evidence.
This is the seed of a larger database. The plan is to add every randomized trial of a classroom practice in K–12, with the same columns, so that a reader never has to go to a second site to check a claim. New studies are logged monthly and reviewed quarterly; see Keeping it current.
21 of 46 studies
- Design
- Review or practice guide
- Grade bands
- K–2, 3–5, 6–8, 9–12, adult
- Subjects
- general
- Sample
- 50 classroom experiments, 5,374 students
- Compared with
- Business as usual
- Found
- 57% of effects were medium or large.
- Limits
- Benefits smaller when final test questions were reworded.
- Design
- Meta-analysis
- Grade bands
- 3–5, 6–8, 9–12, adult
- Subjects
- Math
- Sample
- Random-assignment studies of worked examples in math, most in classrooms
- Compared with
- Problem solving without examples
- Found
- Worked examples improved math performance (g = 0.48), for first learning and for practice.
- Limits
- Effects vary with how examples are paired with practice.
- Principles
- Design
- Comparison study
- Grade bands
- 6–8
- Subjects
- Social studies
- Sample
- 8th grade U.S. history
- Compared with
- Review without testing, or no review
- Found
- After nine months, students who had been tested on the facts remembered more than students who restudied them.
- Limits
- One school; facts only.
- Design
- Review or practice guide
- Grade bands
- adult
- Subjects
- general
- Sample
- Review of memory experiments, mostly adults
- Compared with
- —
- Found
- Working memory holds about 3 to 5 chunks, not 7 plus or minus 2.
- Limits
- Lab tasks with adults; exact limits for children less precise.
- Principles
- Design
- Review or practice guide
- Grade bands
- 6–8, 9–12, adult
- Subjects
- general
- Sample
- Review of ten study techniques
- Compared with
- —
- Found
- Practice testing and spaced practice rated high; rereading and highlighting rated low.
- Limits
- Ratings, not a single pooled effect.
- Design
- Randomized trial
- Grade bands
- 3–5
- Subjects
- Math
- Sample
- About 290 at-risk 4th graders
- Compared with
- School's usual fraction teaching
- Found
- Better on fraction comparison, number line, calculations, and released NAEP items.
- Limits
- At-risk students only.
- Design
- Randomized trial
- Grade bands
- 3–5
- Subjects
- Math
- Sample
- 277 at-risk 4th graders, 49 classrooms, 14 schools
- Compared with
- Usual teaching
- Found
- Gains on NAEP fraction items and number line.
- Limits
- Researcher-developed program.
- Design
- Randomized trial
- Grade bands
- 3–5
- Subjects
- Math
- Sample
- 213 at-risk 4th graders
- Compared with
- Usual teaching
- Found
- Better understanding and calculation; gains explained by better fraction-size understanding.
- Limits
- Small groups, not whole class.
- Design
- Review or practice guide
- Grade bands
- 3–5
- Subjects
- Math
- Sample
- Five trials with at-risk 4th graders
- Compared with
- —
- Found
- Consistent effects across five years of trials.
- Limits
- Same research group.
- Design
- Randomized trial
- Grade bands
- 3–5
- Subjects
- Math
- Sample
- 225 at-risk 4th graders
- Compared with
- Usual teaching
- Found
- Gains transferred to decimals without decimal instruction.
- Limits
- Same research group.
- Design
- Comparison study
- Grade bands
- 6–8
- Subjects
- Science
- Sample
- 8th grade science, one school
- Compared with
- Content not quizzed
- Found
- 13 to 25% gains on unit exams; benefits lasted to semester and end-of-year exams.
- Limits
- One school.
- Design
- Review or practice guide
- Grade bands
- K–2, 3–5, 6–8, 9–12
- Subjects
- general
- Sample
- Review of classroom applications of cognitive science
- Compared with
- —
- Found
- Classroom evidence is thinner than lab evidence; multi-strategy programs tested at scale often showed small effects; little early-years evidence.
- Limits
- Review, not pooled estimates.
- Design
- Lab study
- Grade bands
- adult
- Subjects
- general
- Sample
- College students
- Compared with
- Restudying
- Found
- Restudying won at 5 minutes; testing won at 2 days and 1 week. Students felt more confident after rereading.
- Limits
- Lab, adults, short passages.
- Design
- Comparison study
- Grade bands
- 6–8
- Subjects
- Social studies
- Sample
- 6th grade social studies, one school
- Compared with
- Not quizzed, or content shown twice
- Found
- Better chapter and semester exams after quizzing.
- Limits
- One school.
- Design
- Randomized trial
- Grade bands
- 6–8
- Subjects
- Math
- Sample
- 787 seventh graders, 54 classes, 5 Florida schools
- Compared with
- Mostly blocked practice, same problems
- Found
- 61% vs 38% on an unannounced test a month later (d = 0.83). Meets WWC standards without reservations.
- Limits
- One district, one research group; state-test outcomes untested until the WestEd replication reports (through 2027).
- Design
- Review or practice guide
- Grade bands
- 6–8
- Subjects
- Math
- Sample
- 13,505 problems in six textbooks
- Compared with
- —
- Found
- Under 10% of practice problems were mixed.
- Limits
- Six texts.
- Design
- Comparison study
- Grade bands
- 6–8
- Subjects
- Math
- Sample
- 7th graders, 9 weeks, one school
- Compared with
- Blocked practice
- Found
- 72% vs 38%, even for dissimilar problem types.
- Limits
- One school.
- Design
- Comparison study
- Grade bands
- 6–8
- Subjects
- Math
- Sample
- 126 seventh graders, 3 months
- Compared with
- Blocked practice, same problems
- Found
- Higher on immediate and delayed tests (d = 0.42 and 0.79).
- Limits
- Within-student design.
- Design
- Correlation
- Grade bands
- 3–5, 9–12
- Subjects
- Math
- Sample
- U.S. and U.K. longitudinal samples
- Compared with
- —
- Found
- 5th grade fraction and division knowledge predicted high school algebra and overall math, after accounting for IQ, reading and family income.
- Limits
- Not causal.
- Design
- Lab study
- Grade bands
- 3–5
- Subjects
- Math
- Sample
- 4th graders, prism problems
- Compared with
- Blocked practice
- Found
- 77% vs 38% on a test one day later.
- Limits
- Short delay; lab-like setting.
- Design
- Meta-analysis
- Grade bands
- K–2, 3–5, 6–8, 9–12, adult
- Subjects
- general
- Sample
- 222 classroom studies, about 48,000 students
- Compared with
- Other learning activities or none
- Found
- Quizzing raised achievement by about half a standard deviation across school levels.
- Limits
- Mixed designs and comparison groups.