This paper explores an information intervention designed and implemented within a school assignment mechanism in Mexico City. Through a randomized experiment, we show that providing a subset of applicants with feedback about their academic performance can enhance sorting by skill across high school tracks. We embed the experimental variation into an empirical model of schooling choice and outcomes to assess the impact of the intervention for the overall population of applicants. Feedback provision is shown to increase the efficiency of the student school allocation, while congestion externalities are detrimental for the equity of downstream education outcomes.