Education reform is top of the agenda of almost every country in the world. Yet despite massive increases in spending (last year, the world’s governments spent $2 trillion on education) and ambitious attempts at reform, the performance of many school systems has barely improved in decades. This is all the more surprising because there are wide variations in the quality of education. For instance, in international assessments, less than one percent of African and Middle Eastern children perform at or above the Singaporean average. Nor is this solely the result of the level of investment. Singapore, one of the world's top performers, spends less on primary education than do 27 of the 30 countries in the OECD. Changing what happens in the hearts and minds of millions of children -the main charge of any school system -is no simple task. That some do so successfully while others do not is indisputable. So why is it that some school systems consistently perform better and improve faster than others?