Social inequality in education is universally observed in countries in which children are brought up in unequal families; they enter school with unequal linguistic, cognitive, and cultural assets and attain unequal levels of achievement. Moreover, they make unequal choices, leading to unequal levels of education and social reproduction. However, the latter varies across countries, demonstrating that the way school itself is organized matters. The timing of the selection process and the degree of segregation within the system are especially important, along with the student social mix they generate. As countries implement policies to fight educational inequality, simply expanding education does not prove efficient since it only delays social selection. More qualitative policies then seem necessary, such as limiting early inequalities and focusing on disadvantaged families, which in turn requires broader social policies.