This article focusses on the evolution of the school governance model in Spain since the 1980s. In Spain and elsewhere in Europe, the state's monopoly over education has softened and new forms of educational governance have emerged. This has resulted in the decentralization of decision-making authority to individual schools, municipalities, and regions and a significant increase in school autonomy. We explore from a political science perspective how partisan preferences and teachers unions have decisively shaped the reform trajectory. We show that leftist and center-right governments and different teachers' unions have promoted different versions of school autonomy in line with their ideological rationales, resulting in a reconfiguration of the school governance model with each change in government.