Are Parents Gaming their School Assignment?
School Assignment, January 2011
In a study of school admissions systems, Parag Pathak and Tayfun Sonmez introduce a method to compare the mechanisms which districts use to assign students to seats based on their vulnerability to manipulation and offer insight into district policy changes in case studies of Chicago Public Schools’ abandonment of their old assignment mechanism in 2009 and England’s nationwide ban on the popular Boston mechanism in 2007.
Recent admissions reforms have been based in part on the desire to simplify the strategic aspects of the admissions process for participants. However, unlike admissions reforms in Boston and New York City, changes to how students are matched to seats in Chicago and England did not involve the direct intervention of economists. As a result, these changes provide some indication of how policymakers and the public perceive particular methods of student assignment. In particular, officials from Chicago Public Schools changed their assignment mechanism for coveted spots at selective college preparatory high schools midstream. After asking about 14,000 applicants to submit their preferences for schools under one mechanism, the district asked they re-submit their preferences under a new mechanism. Officials were concerned that “high-scoring kids were being rejected simply because of the order in which they listed their college prep preferences” under the abandoned mechanism. What is somewhat puzzling is that the new mechanism is also manipulable. This paper introduces a method to compare mechanisms based on their vulnerability to manipulation. Under this notion, the old mechanism is more manipulable than the new Chicago mechanism. Indeed, the old Chicago mechanism is at least as manipulable as any other plausible mechanism. A number of similar transitions between mechanisms took place in England after the widely popular Boston mechanism was ruled illegal in 2007. The study’s approach provides support for these and other recent policy changes involving the way children obtain school seats.