Policymakers considering school choice need to understand how it affects students who attend schools of choice, but they should also account for its effect on students who remain in traditional public schools. Recent work has summarized the evidence on how school choice affects students who participate. In contrast, this brief describes key findings on how two types of school choice—charter schools and private school vouchers—affect student achievement in traditional public schools. The brief also addresses the implications of this evidence for policymakers and proposes next steps for research.