The universalization of basic education was set to be one of the great policy successes of the twentieth century, yet millions are still unenrolled, and many of those who attended school learned little. The ‘learning crisis’ now dominates the global education policy agenda, yet little is understood of why education quality reforms have had so little success compared to earlier expansionary reforms. This chapter sets out the rationale for this book, which is to explore how the nature of the political settlement or distribution of power between contending social groups in a given country shapes efforts to get learning reforms on the policy agenda, how they are implemented, and what difference they make to what children learn. It discusses debates about the sources and determinants of the learning crisis, examining its extent and nature and providing a rationale for the key themes the book takes up in subsequent theoretical, empirical, and comparative chapters.