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.
14 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
- Meta-analysis
- Grade bands
- adult
- Subjects
- general
- Sample
- 317 experiments
- Compared with
- Massed practice
- Found
- Spacing helps; the longer you need to remember, the longer the best gap between sessions.
- Limits
- Mostly lab, verbal materials.
- 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
- Lottery study
- Grade bands
- 3–5, 6–8
- Subjects
- Reading and ELA, Social studies, Science
- Sample
- 2,310 applicants to 9 Colorado Core Knowledge charters
- Compared with
- Lottery losers who attended other schools
- Found
- About 16 percentile points higher in reading in grades 3–6; income gap closed at the one low-income school.
- Limits
- Charter schools, so curriculum and school model came together.
- Design
- Randomized trial
- Grade bands
- K–2
- Subjects
- Reading and ELA, Science, Social studies
- Sample
- 30 schools, nearly 3,000 students
- Compared with
- Business as usual
- Found
- Science reading comprehension up (0.18); smaller summer losses.
- Limits
- Overall district reading score not significant in the WWC review.
- 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
- 6–8
- Subjects
- Reading and ELA
- Sample
- 64 seventh and eighth graders
- Compared with
- Students with less baseball knowledge
- Found
- Baseball knowledge, more than reading ability, predicted comprehension of a baseball text.
- Limits
- Small; disputed in later critiques.
- 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
- Correlation
- Grade bands
- K–2, 3–5
- Subjects
- Social studies, Reading and ELA
- Sample
- ECLS-K 2011 national data
- Compared with
- Less social studies time
- Found
- More social studies time linked to better reading; more ELA time was not.
- Limits
- Not causal.
- 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.