Most education around the globe is public. Moreover, invest rates in education as well as schooling attainment differ substantially across countries. We construct a general equilibrium life-cycle model that is consistent with these facts. We provide simple analytical solutions for the optimal educational choices, which may entail pure public provision of education, and their general equilibrium effects. We calibrate the model to fit cross-country differences in demographic and educational variables. The model is able to replicate a number of key regularities in the data beyond the matching targets. We use the model to identify and quantify sources of world income differences, and find that demographic factors, in particular mortality rates, explain most of the differences. We also use the model to study the role of public education, and the effects of the HIV/AIDS pandemic in development.