Gender Composition, Spillover Effects and Students' Outcomes: Evidence from Classmates' Siblings

This paper uses data from the random classroom assignment sample of the China Education Panel Survey to examine the spillover effects of classmates' siblings' gender composition on students' outcomes. We find that a higher proportion of female siblings among classmates is associated with significant improvements in students' academic performance, cognitive skills, and non-cognitive skills. These results remain robust after accounting for potential reflection problems and omitted variable concerns. We further explore the underlying mechanisms and show that students' effort and learning attitudes serve as key mechanisms through which the gender composition of classmates' siblings generates spillover effects, with student diligence playing a particularly central role. In addition, explanatory power analyses indicate that students' effort and learning attitudes account for a substantial share of the observed effects. This study provides a new perspective for understanding the impact of gender composition on human capital accumulation.