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.
5 of 46 studies
- 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
- 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.