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Priorities vs. Precedence in School Choice: Theory and Evidence from Boston ∗

A central issue in school choice is the debate over who obtains seats at oversubscribed schools. Choice plans in many cities grant students higher priority for some seats at their neighborhood schools. This paper demonstrates how the precedence order, i.e. the order in which seats are depleted by applicants with specific claims, is a lever to achieve distributional goals that has effects comparable to priorities under the deferred acceptance algorithm. While Boston gives priority to neighborhood applicants for half of each school’s seats, the intended effect of this policy is almost entirely lost because of the seat precedence order; its outcome is nearly equivalent to that of a mechanism without any neighborhood priority. A change in precedence, holding fixed the current 50-50 school seat split, corresponds to almost three-quarters of the effect of switching from 0% to 100% neighborhood priority. We formally establish that either increasing the number of neighborhood priority seats at a school or adjusting the precedence of neighborhood seats have the same qualitative effect: an increase in the number of neighborhood students assigned to that school. Decisions about precedence have distributional effects with little impact on the overall number of students who receive their top choices and therefore are inseparable from decisions about priorities. Transparency about how precedence unintentionally undermined neighborhood priority is a major reason neighborhood priority was abandoned in Boston in 2013.