This paper uses cross-national data to examine the effects of different dimensions of decentralization on the efficiency of educational policies in OECD countries. The results show that the autonomy of subnational governments, both on the expenditure and revenue sides of their activities, is what really matters in determining the effect of decentralization on educational outcomes. The decision-making autonomy of subnational governments with regard to the regulation and management of the educational system has a significant and positive effect on educational attainment, though this varies with the degree to which subnational governments are held accountable for their taxing decisions. These results are robust to the different analyses conducted, thus corroborating that they are not driven by the potential endogeneity of decentralization policies.