The Demise of Walk Zones in Boston: Priorities vs. Precedence in School Choice

School choice plans in many cities grant students higher priority for some (but not all) seats at their neighborhood schools. This paper demonstrates how the precedence order, i.e. the order in which different types of seats are filled by applicants, has quantitative effects on distributional objectives comparable to priorities in the deferred acceptance algorithm. While Boston's school choice plan gives priority to neighborhood applicants for half of each school's seats, the intended effect of this policy is lost because of the precedence order. Despite widely held impressions about the importance of neighborhood priority, the outcome of Boston's implementation of a 50-50 school split is nearly identical to a system without neighborhood priority. We formally establish that either increasing the number of neighborhood priority seats or lowering the precedence order positions of neighborhood seats at a school have the same effect: an increase in the number of neighborhood students assigned to the school. We then show that in Boston a reversal of precedence with no change in priorities covers almost three-quarters of the range between 0% and 100% neighborhood priority. Therefore, decisions about precedence are inseparable from decisions about priorities. Transparency about these issues--in particular, how precedence unintentionally undermined neighborhood priority--led to the abandonment of neighborhood priority in Boston in 2013.