Sibling Spillovers: Having an Academically Successful Older Sibling May be More Important for Children in Disadvantaged Families

Abstract

This paper examines causal sibling spillover effects among socially advantaged (e.g. white, two-parent, or non-poor school district) and disadvantaged families (e.g. black, single-mother, or poor school district) in elementary and middle school. Exploiting discontinuities in school starting age created by North Carolina school entry laws, we adopt a quasi-experimental approach and compare test scores of public school students whose older siblings were born shortly before and after the school entry cutoff date. We find that individuals whose older siblings were born shortly after the school entry cutoff date have significantly higher scores in middle school, and that this positive spillover effect is particularly large among disadvantaged families. We estimate that these spillover effects account for more than one third of observed statistical associations in test scores between siblings, and the magnitude is much larger for disadvantaged families than advantaged families. Our results suggest that educational spillover effects from older to younger siblings lead to greater divergence in academic outcomes between families.