Why Change School Choice Mechanisms?

Discussion Paper

Atila Abdulkadiroglu, Parag A. Pathak, Alvin E. Roth, Tayfun Sonmez

May 2006

In a closer examination of the school choice mechanism previously used by Boston Public Schools, Abdulkadiroglu, Pathak, Roth, and Sönmez establish an empirical case against the previous Boston mechanism in favor of a change to a strategy-proof mechanism.  While some parents use sophisticated strategic behavior, others display unsophisticated strategic behavior.  Without knowing the true preferences of a family, there arises a mistake causing families to be disproportionately unassigned.

The Boston School Committee voted to replace the existing school choice mechanism (the Boston mechanism) with an alternative mechanism that removes the incentives to “game the system.” This followed two years of intensive discussion and analysis of the existing school choice system and the behavior it elicited, as well as a discussion of two different possible replacement school choice mechanisms.

The Boston experience has implications for other school districts.  There are quite a few other school districts with student assignment systems sharing the main features of the Boston mechanism – for example Cambridge, Charlotte-Mecklenberg, Denver, Miami-Dade, Rochester, Tampa-St. Petersburg, and White Plains. Based on our analysis of the behavior of Boston families, it seems likely that in these other school districts parents are faced with solving a complex strategic problem, rather than just a problem of forming preferences over schools. A strategy-proof mechanism like the ones presented in this study would lift this strategic burden from parents, and makes the school choice process more transparent. School choice is often a sensitive political issue, and transparency helps to remove some aspects of how to best assign children to schools from the political arena to the technical arena, and clarify which issues remain to be settled by the political process. There will always be such issues, since until there are enough top quality school places to satisfy all families, some aspects of school choice will be a distributive process, with only some students able to gain admission to the most desirable schools.