This new review study by Saiying Steenbergen-Hu, Matthew C. Makel, Paula Olszewski-Kubilius published in Review of Educational Research looked at two meta-analyses on ability grouping and acceleration and I am personally glad because the insights in our book are confirmed.
Abstracts of studies are sometimes not so good, but this is a clear summary:
Two second-order meta-analyses synthesized approximately 100 years of research on the effects of ability grouping and acceleration on K–12 students’ academic achievement. Outcomes of 13 ability grouping meta-analyses showed that students benefited from within-class grouping (0.19 ≤ g ≤ 0.30), cross-grade subject grouping (g = 0.26), and special grouping for the gifted (g = 0.37), but did not benefit from between-class grouping (0.04 ≤ g ≤0.06); the effects did not vary for high-, medium-, and low-ability students. Three acceleration meta-analyses showed that accelerated students significantly outperformed their nonaccelerated same-age peers (g = 0.70) but did not differ significantly from nonaccelerated older peers (g = 0.09). Three other meta-analyses that aggregated outcomes across specific forms of acceleration found that acceleration appeared to have a positive, moderate, and statistically significant impact on students’ academic achievement (g = 0.42).
From the conclusion:
Stanley (2000, p. 221) said that education should “avoid trying to teach students what they already know.” Based on the nearly century’s worth of research findings presented here, we believe that the data clearly suggest that ability grouping and acceleration are two such strategies for achieving this goal. The current findings will not settle all controversies on the philosophy of education. Nevertheless, we believe that they help clarify the academic effects of ability grouping and acceleration. Regardless, the conversation needs to evolve beyond whether such interventions can ever work. There is not an absence of evidence, nor is there evidence of absence of benefit. The preponderance of existing evidence accumulated over the past century suggests that academic acceleration and most forms of ability grouping like cross-grade subject grouping and special grouping for gifted students can greatly improve K–12 students’ academic achievement.