Boston Public Schools replaced its gameable assignment rule with strategy-proof matching

Boston's public school assignment used a priority mechanism: a school took applicants who listed it first, then moved to second choices. Because being first on the list mattered, parents had to strategize — listing a popular school first could leave a child unassigned if that school filled up.

Market-design researchers Abdulkadiroğlu, Pathak, Roth and Sönmez analyzed the mechanism and showed it rewarded sophisticated parents and hurt unsophisticated ones; many unassigned students could have been placed at one of their stated choices with a different ranking. Their 2005 American Economic Review paper and 2006 NBER study laid out the case for a strategy-proof alternative.

In July 2005 the Boston School Committee voted to replace the old rule with a deferred acceptance mechanism, which makes truthful preference lists a dominant strategy. The change simplified the strategic problem facing parents and removed the penalty for honest ranking.

Make rankings safe to state honestly

Honest rankings become a dominant strategy, so families stop needing to guess about other parents' behavior.

The fairness argument — sophisticated parents gaming while others were not — made the case for change compelling.

The same deferred acceptance logic later spread to other districts, showing the design transfers.

When a rule rewards strategic guessing, the people who suffer are those who do not game it — switching to a strategy-proof mechanism is a fairness fix, not just an efficiency one.

Boston's new mechanism has run since 2005 and became a canonical market-design case; the same team went on to design New York City's high school match and advise New Orleans' OneApp, as the New Orleans paper itself records. The episode is a standard reference for why strategy-proofness is an equity property, not just a technical one.