The extensive research literatures on educational peer effects and on factors affecting college choice have remained largely separate. We connect them by estimating the impact of older siblings’ college choices on the college choices of their younger siblings. Data from the College Board allow us to identify the college choices of all SAT-takers from 2004-14 and those of any younger siblings in the data. We use the data to uncover dozens of colleges that hide from applicants the use of SAT thresholds in the admissions process. A regression discontinuity design shows such thresholds generate exogenous variation in older siblings’ college access and enrollment. We then show that older siblings’ increased college access raises younger siblings’ college enrollment rates, particularly for families with low ex ante probabilities of four-year college enrollment. Such within-family spillover effects suggest that college-going behavior is transmissible between peers.