We study sibling spillover effects on the school performance of the elder sibling from the younger sibling using data on multi-children households in rural China. We use the variation in the younger sibling's schooling status to parse out the spillover effects and exploit the arbitrary school enrollment eligibility cutoff dates imposed by the Chinese Law of Compulsory Education as exogenous variation in the timing of school enrollment. We find a significant increase in school test scores of elder siblings when their younger siblings begin school. The strongest spillover effects occur when the younger sibling is a girl. Such increases in test scores come from a more intense academic atmosphere within a household when both children enroll in school and are not attributed to differential parental education investments or attitudes. Our findings suggest that policies promoting girls' education, pre-elementary school age education programs, and after school public resources can have multiplier effects through sibling spillovers.