The studies
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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.
4 of 46 studies
- 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
- 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
- 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
- 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.