Comparing Achievement between K–8 and Middle Schools: A Large‐Scale Empirical Study

This study compares middle schools to K–8 schools, as well as to newly formed K–8 schools that are part of a K–8 conversion policy. The outcome is student achievement, and our sample includes 40,883 eighth‐grade students from 95 schools across five cohorts. The analysis uses multilevel modeling to account for student, cohort, and school‐level variation, and it includes statistical controls for both population demographics and school characteristics. The results find that older K–8 schools perform significantly better than middle schools, and this advantage is explained by differing student and teacher populations, average grade size, and school transition. Newer K–8 schools did not enjoy the same advantage despite having smaller grades and lower transition rates, due to their more disadvantaged populations.