Boundary Defense: Evidence from a Referendum Against School Reform

Policies that reinforce unequal opportunity persist in democracies. I develop a theory of ``Boundary Defense" to explain why. Middle-class families mobilize to defend these opportunity boundaries against reform when they lack alternative strategies to secure their status against uncertainty. In Germany, I argue early-age sorting across stratified schools is an opportunity boundary that excludes immigrants and that status uncertain German families defend it against reform. To test this, I introduce a 2010 referendum which blocked a reform to early-age sorting across schools in Hamburg and collect data from precinct-level votes, city-district demographics, election studies, and archival sources. Results show referendum support was highest in lower-income places and specific precincts with less access to academic schools and higher shares of immigrant children, among parents of school-age children without academic educations, and predicts future support for politicians who took positions against the reform. I suggest this theory also applies to different boundaries in both education and other fields, and that policies which reduce middle-class uncertainty can equalize opportunity better than technocratic reforms given boundary defense.