Recent evidence using compulsory schooling laws as instruments for education suggests that education has a causal effect on mortality (Lleras-Muney, 2005). However, little is known about how exactly education affects health. This paper uses compulsory schooling laws to try to identify how education impacts health and to indirectly assess the merit of using these laws to infer the causal effect of education on health. I find that previous Census mortality results are not robust to the inclusion of state-speci...fic time trends but that robust effects of education on general health status can be identified using individual level data in the SIPP. However, the pattern of effects for specific health conditions in the SIPP appears to depart markedly from prominent theories of how education should affect health. I also find that vaccination against smallpox for school age children may account for some of the improvement in health and its association with education. These results raise concerns about using early century compulsory schooling laws to identify the causal effects of education on health.