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.
23 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
- K–2, 3–5
- Subjects
- Reading and ELA
- Sample
- Same studies as Ehri 2001
- Compared with
- Same
- Found
- Smaller but still positive effect, about d = 0.24.
- Limits
- Different coding choices.
- 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
- Meta-analysis
- Grade bands
- K–2, 3–5
- Subjects
- Reading and ELA
- Sample
- 38 experiments, 66 comparisons
- Compared with
- Unsystematic or no phonics
- Found
- d = 0.41; 0.55 when started early, 0.27 after first grade; effects lasted after instruction ended.
- Limits
- Mix of experimental and quasi-experimental studies.
- Design
- Trend data
- Grade bands
- K–2
- Subjects
- Reading and ELA
- Sample
- All Year 1 pupils in England
- Compared with
- Earlier years
- Found
- 58% met the standard in 2012, 82% in 2018.
- Limits
- Not causal; schools learn the test.
- 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
- 9–12
- Subjects
- Math
- Sample
- About 2,600 and 2,700 Chicago 9th and 10th graders, two trials
- Compared with
- Business as usual
- Found
- Math scores up 0.18 to 0.40 SD; effects lasted into later years.
- Limits
- High school math only; one city.
- Design
- Review or practice guide
- Grade bands
- K–2, 3–5
- Subjects
- Reading and ELA
- Sample
- Expert panel review of rigorous studies
- Compared with
- —
- Found
- Strong evidence for sound-letter links and decoding; moderate for daily connected text; minimal for academic language.
- Limits
- Panel judgments.
- 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
- K–2, 3–5, 6–8
- Subjects
- Reading and ELA, Math
- Sample
- Over 6,800 students across three years
- Compared with
- Students not tutored, often getting other small-group help
- Found
- Reading up 0.04 to 0.09 SD; no average effect in math or grades.
- Limits
- Many sessions before or after school; program changing as it scaled.
- 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
- Trend data
- Grade bands
- 3–5
- Subjects
- Reading and ELA, Math
- Sample
- 4th graders, state results
- Compared with
- Other states, demographics-adjusted
- Found
- First in the nation in 4th grade reading and math after adjustment; 49th in reading in 2013.
- Limits
- Not causal; many reforms at once.
- Design
- Meta-analysis
- Grade bands
- K–2, 3–5, 6–8, 9–12
- Subjects
- Reading and ELA, Math
- Sample
- 89 randomized trials
- Compared with
- No tutoring
- Found
- 0.29 SD average; largest with teachers or aides, early grades, 3+ days a week, during school.
- Limits
- Mostly pre-pandemic, smaller programs.
- 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
- Review or practice guide
- Grade bands
- K–2, 3–5, 6–8
- Subjects
- Reading and ELA, Math
- Sample
- Review of progress-monitoring studies
- Compared with
- —
- Found
- Achievement improved when teachers used progress data to change instruction; collecting it alone did little.
- Limits
- Mostly special education settings.
- Design
- Review or practice guide
- Grade bands
- K–2, 3–5
- Subjects
- Reading and ELA
- Sample
- Response to the reanalyses
- Compared with
- —
- Found
- Effects of the reanalyzed size still matter in practice.
- Limits
- Commentary.
- 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.