  Recently dozens of school districts and college admissions systems around the
world have reformed their admission rules. As a main motivation for these
reforms the policymakers cited strategic flaws of the rules: students had
strong incentives to game the system, which caused dramatic consequences for
non-strategic students. However, almost none of the new rules were
strategy-proof. We explain this puzzle. We show that after the reforms the
rules became more immune to strategic admissions: each student received a
smaller set of schools that he can get in using a strategy, weakening
incentives to manipulate. Simultaneously, the admission to each school became
strategy-proof to a larger set of students, making the schools more available
for non-strategic students. We also show that the existing explanation of the
puzzle due to Pathak and S\"onmez (2013) is incomplete.
