Research Design Meets Market Design: Using Centralized Assignment for Impact Evaluation∗

A growing number of school districts use centralized assignment mechanisms to allo-cate school seats in a manner that reflects student preferences and school priorities. Many of these assignment schemes use lotteries to ration seats when schools are oversubscribed. The resulting random assignment opens the door to credible quasi-experimental research designs for the evaluation of school effectiveness. Yet the question of how best to separate the lottery-generated variation integral to such designs from non-random preferences and priorities remains open. This paper develops easily-implemented empirical strategies that fully exploit the random assignment embedded in widely-used mechanisms such as deferred acceptance. We use these new methods to evaluate charter schools in Denver, one of a growing number of districts that integrate charter and traditional public schools in a uni-fied assignment system. The resulting estimates show large achievement gains from charter school attendance. Our approach generates substantial efficiency gains over ad hoc methods that fail to exploit the full richness of the lotteries generated by centralized assignment with random tie-breaking. ∗We thank Alisha Chiarelli, Brian Eschbacher, Van Schoales, and the staff at Denver Public Schools answering our questions and facilitating access to data. Peter Hull, Hide Ichimura, Guido Imbens, Rafael Lalive, Edward Lazear, Anna Mikuscheva, Chris Walters and seminar participants at SOLE and Stanford University and in Japa