Much of the research on the economic impact of education has properly concentrated on the role of school attainment—that is, the quantity of schooling.This focus is natural.The revolution in the United States during the 20th century was the universal provision of a basic education. Moreover, years of schooling are easily measured, and data on years attained, both over time and across individuals, are readily available. Yet today’s policy concerns revolve around issues of quality much more than of quantity.