We present a new data set for years of schooling across countries for the 1960-2000 period. The series are constructed from the OECD database on educational attainment and from surveys published by UNESCO. Two features that improve the quality of our data with respect to other series, particularly for series in first-differences, are the use of surveys based on uniform classification systems of education over time, and an intensified use of information by age groups. As a result of the improvement in quality, these new series can be used as a direct substitute for Barro and Lee's (2001; Oxford Economic Papers, 3, 541-563) data in empirical research. In standard cross-country growth regressions we find that our series yield significant coefficients for schooling. In panel data estimates our series are also significant even when the regressions account for the accumulation of physical capital. Moreover, the estimated macro return is consistent with those reported in labour studies. These results differ from the typical findings of the earlier literature and are a consequence of the reduction in measurement error in the series.