More than half the variance in length of school session in a cross section of 329 localities in Massachusetts in 1855 can be explained by the share of Irish in the town's population, the family per dwelling ratio, and a proxy for the share of male merchants over 15 in the population, all of which enter regression equations with strong positive coefficients. This paper considers what these results may tell us about a number of hypotheses that link industrialization and educational revitalization in antebellum Massachusetts, discusses independent confirmation of these basic relationships, and concludes with a more general discussion of the implications of this Massachusetts evidence.