Few school choice evaluations consider students who leave such programs, and fewer still consider the effects of leaving these programs as policy-relevant outcomes. Using a representative sample of students from the citywide voucher program in Milwaukee, Wisconsin, we analyze more than 1,000 students who leave the program during a 4-year period. We show that low-performing voucher students tend to move from the voucher sector into lower performing and less effective public schools than the typical public school student attends, whereas high-performing students transfer to better public schools. In general, transferring students realize substantial achievement gains after moving to the public sector; these results are robust to multiple analytical approaches. This evidence has important implications for school choice policy and research. (Contains 21 notes, 7 tables, and 1 figure.)