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.
22 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
- Randomized trial
- Grade bands
- K–2
- Subjects
- Math
- Sample
- 110 elementary schools, 12 districts, grades 1–2
- Compared with
- Four curricula against each other
- Found
- Math Expressions, Saxon, and SFAW/enVision all outperformed Investigations by end of grade 2.
- Limits
- Early grades; older editions.
- Design
- Meta-analysis
- Grade bands
- K–2, 3–5, 6–8, 9–12, adult
- Subjects
- general
- Sample
- 164 studies
- Compared with
- Unassisted discovery vs explicit teaching; enhanced discovery vs other methods
- Found
- Explicit teaching beat unassisted discovery; guided or enhanced discovery beat other methods.
- Limits
- Includes adult and university studies; "enhanced discovery" is broad.
- Principles
- Design
- Comparison study
- Grade bands
- 3–5
- Subjects
- Math
- Sample
- Nearly 6,000 schools, grades 4–5
- Compared with
- Schools using other textbooks
- Found
- Little difference in average math gains by textbook; more variation where texts were used more.
- Limits
- Not randomized; low PD and partial use.
- 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
- 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
- 6–8
- Subjects
- Math
- Sample
- 363 teachers, about 27,600 Virginia middle school students
- Compared with
- No lessons or support
- Found
- Lessons plus support: +0.086 SD; lessons alone smaller and not consistently significant.
- Limits
- Inquiry-oriented lessons; not a test of explicit vs inquiry.
- Design
- Randomized trial
- Grade bands
- 3–5
- Subjects
- Science
- Sample
- 112 third and fourth graders
- Compared with
- Direct instruction vs discovery learning of experiment design
- Found
- 77% mastered fair-test design after direct instruction vs 23% by discovery; transfer was equal for those who mastered it.
- Limits
- Single lab-style study; short task.
- Principles
- 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
- 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
- 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
- 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
- Meta-analysis
- Grade bands
- 6–8, 9–12, adult
- Subjects
- Math, Science
- Sample
- 53 studies
- Compared with
- Instruction first
- Found
- Problem solving before instruction helped conceptual understanding, mostly for secondary and university students, less for primary.
- Limits
- Contested; applies to students who already have the basics.
- Principles
- 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.