School-choice policies are expected to generate healthy competition between schools, leading to improvements in school quality and better outcomes for students. However, the empirical literature testing this assumption yields mixed findings. This systematic review and meta-analysis tests this theory by synthesizing the empirical literature on the competitive effects of school choice on student achievement. Overall, we found small positive effects of competition on student achievement. We also found some evidence that the type of school-choice policy and student demographics moderated the effects of competition on student achievement. By examining whether school competition improves outcomes, our findings can inform decisions of state and local policymakers who have adopted or are considering adopting school-choice reforms.