Across countries, education and democracy are highly correlated. We motivate empirically and then model a causal mechanism explaining this correlation. In our model, schooling teaches people to interact with others and raises the benefits of civic participation, including voting and organizing. In the battle between democracy and dictatorship, democracy has a wide potential base of support but offers weak incentives to its defenders. Dictatorship provides stronger incentives to a narrower base. As education raises the benefits of civic engagement, it raises participation in support of a broad-based regime (democracy) relative to that in support of a narrow-based regime (dictatorship). This increases the likelihood of successful democratic revolutions against dictatorships, and reduces that of successful anti-democratic coups.