The Long Reach of Targeted Smaller Classes: Evidence from a National Reform

This paper examines whether the effects of class size reduction in early primary grades persist through entry to middle school. I exploit France's national reform, launched in 2017, which halved grade 1 and grade 2 class sizes in disadvantaged schools and produced positive and significant effects on French and mathematics achievement by the end of second grade. Using administrative data spanning nine cohorts of students entering sixth grade from 2017 to 2025, I employ an event study design comparing the evolution of sixth-grade outcomes between students exposed to smaller classes in early grades and those who were not. I find no effect on French, but a positive effect on mathematics, particularly in the most disadvantaged schools. In these schools, the effect increases across successive treated cohorts, reaching 0.078 standard deviations for the fourth cohort. This gain closes approximately 12% of the pre-reform mathematics achievement gap between disadvantaged and non-disadvantaged schools at sixth-grade entry. The reform is also associated with a small increase in students' self-reported readiness to succeed. These findings suggest that class size reduction, when targeted at the students expected to benefit most, produces effects that persist well beyond the early grades in which it was implemented.