Girls’ school participation has expanded considerably in the developing world over the last few decades, a phenomenon expected to have substantial consequences for reproductive behaviour. Using Demographic and Health Survey data from 43 countries, this paper examines trends and differentials in the mean ages at three critical life-cycle events for young women: first sexual intercourse, first marriage, and first birth. We measure the extent to which trends in the timing of these events are driven either by the changing educational composition of populations or by changes in behaviour within education groups. Mean ages have risen over time in all regions for all three events, except age at first sex in Latin America and the Caribbean. Results from a decomposition exercise indicate that increases in educational attainment, rather than trends within education groups, are primarily responsible for the overall trends. Possible explanations for these findings are discussed.