This study assesses the impact nationalism has on public policies in ethno-linguistically divided societies. In particular, focus is on the institutional changes from nation-wide systems to Flemish and Francophone halves in Belgian education and mass media. The explanation is a society-based one, which highlights the impact of society on institutions rather than the more common opposite. Evidence demonstrates the role played by the ethno-linguistic structure in promoting the direction of change. Many issues which divide societies and engender political partisanship were subsumed under the question communautaire until a sufficient degree of congruence between the underlying social structure and political institutions was attained.