What One Hundred Years of Research Says About the Effects of Ability Grouping and Acceleration on K–12 Students’ Academic Achievement
We checked this card's citation and the finding we state against the source's own page or record in October 2026.
What it found
Students benefited from grouping within a class, from grouping across grades for a subject, and from special grouping for the gifted, but not from being sorted into separate classes by ability; effects were similar for high-, middle- and low-ability students. Accelerated students outperformed same-age peers who weren't accelerated.
Effect size, as the source reports it: within-class grouping 0.19 ≤ g ≤ 0.30; cross-grade subject grouping g = 0.26; between-class grouping 0.04 ≤ g ≤ 0.06.
What kind of study it is
- Design
- Meta-analysis
- Weight
- A synthesis: it pools or weighs many studies, so it carries the most weight on the evidence meter.
- Sample
- Two second-order meta-analyses: 13 ability grouping meta-analyses and 6 acceleration meta-analyses
- Who
- School-age children (K–12)
Read it
doi.org/10.3102/0034654316675417
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Cited in the Library
Cite this study
Checked against the source in October 2026. All studies · How we rate the evidence · Something wrong? Tell us.