This paper provides an integrated analysis of within- and between-group specific trends in educational inequality. Using the IIASA/VID dataset of populations by age, sex and level of education, I calculate education Gini coefficients and decompose the overall degree of educational inequality into age, sex and within-group components for 171 countries from 1970 to 2010. I analyse the relative relevance of these components for inequality reduction and investigate the distributional outcomes of educational expansion. I use South Asia for a case study as countries in the region are among the most unequal in the world regarding their distributions of education between and within population groups. Generally, I find that equalization between males and females, younger and older cohorts as well as within these subgroups of the population has significantly contributed to declining educational inequality over the observed sample period around the globe. But the relative role of these components fluctuates in the process of educational expansion. First, as improvements are initiated by enhancing the educational opportunities of the youth, the gap between cohorts widens in transition phases but vanishes thereafter. Second, gaps between sexes have been reduced but are predicted to widen again if either males or females are the first to enter higher education levels. To a lesser extent, this is also true for gaps within population subgroups which can be due to the ethnic background or the social and economic status of people. Instead of a Kuznets-curve relation, I thus find evidence for education inequality to evolve in waves as education expands.