Performance Trajectories and Performance Gaps as Achievement Effect-Size Benchmarks for Educational Interventions

TLDR: In this paper, two complementary approaches to developing empirical benchmarks for achievement effect sizes in educational interventions are explored, characterizing the natural developmental progress in achievement made by students from one year to the next as effect sizes.

Abstract: Two complementary approaches to developing empirical benchmarks for achievement effect sizes in educational interventions are explored. The first approach characterizes the natural developmental progress in achievement made by students from one year to the next as effect sizes. Data for seven nationally standardized achievement tests show large annual gains in the early elementary grades followed by gradually declining gains in later grades. A given intervention effect will therefore look quite different when compared to the annual progress for different grade levels. The second approach explores achievement gaps for policy-relevant subgroups of students or schools. Data from national- and district-level achievement tests show that, when represented as effect sizes, student gaps are relatively small for gender and much larger for economic disadvantage and race/ethnicity. For schools, the differences between weak schools and average schools are surprisingly modest when expressed as student-level e...