Syntes: Ruitenburg et al. (2026) — in real school classrooms, retrieval g = 0.37, spacing g = 0.20, interleaving g = 0.40, with boundaries

Källa: Ruitenburg, S. K., Goos, M., Lambert, G., Kirschner, P. A., Jarodzka, H. & Camp, G. (2026). A Meta-Analysis of the Effectiveness and Boundary Conditions of Retrieval Practice, Distributed Practice, and Interleaved Practice in Authentic School Classrooms. Educational Psychology Review 38, 137 (published 29 October 2026). https://doi.org/10.1007/s10648-026-10225-5

Verified content

• [full text] Inclusion: experiments with typically developing pupils aged 6–18 in regular schools; active comparison condition; curricular content; practice and test in school under supervision; random assignment or matched classes; equal time and retention interval across conditions.
• [full text] Retrieval practice g = 0.37 (95% CI 0.18–0.56; 31 studies, 120 effect sizes, 3,391 pupils); significant for factual knowledge (g = 0.53) but not conceptual, procedural or mixed; not significant for comprehension or transfer outcomes.
• [full text] Distributed practice g = 0.20 (95% CI 0.03–0.36; 15 studies, 56 effect sizes, 2,010 pupils); against massed practice g = 0.39, against less-distributed practice not significant; retention interval 1 day–1 week g = 0.21 (p = .06), over 1 week g = 0.24, under 1 hour not significant; significant only when the gap between sessions was 10–100% of the retention interval (g = 0.31).
• [full text] Interleaved versus blocked practice g = 0.40 (95% CI 0.10–0.71; 10 studies, 57 effect sizes, 1,902 pupils); significant with no feedback (g = 0.25) and delayed feedback (g = 0.82, 5 effect sizes), not with immediate feedback (p = .75). The authors call the feedback explanation conjecture.
• [full text] Egger tests showed no publication bias for any of the three strategies; only one dissertation met the criteria.

Limits

• [assessment] Few eligible classroom studies; sparse moderator cells (10 estimates rest on 10 or fewer effect sizes); interleaving mostly procedural maths.
• [assessment] Tests C11's kill line in school classrooms (survived 2026-11-03); the retrieval-practice results are also relevant to C0 (lead noted, not used tonight).

Why it is in the library

The first meta-analysis restricted to authentic primary and secondary classrooms for all three practice strategies.

Added 2026-11-03 by the project (nightly attacks; read: full text). [abstract] = from the published abstract; [full text] = read in the full text; [assessment] = the project's own assessment.