Abstract: The article describes the emergence and development of positive epistemology and quantification tools in the dynamics of inequalities in education. It contributes to a history of the present at a time when datafication and experimentalism are reappearing in educational policies to justify the reduction of inequalities across international surveys and randomised controlled trials. This socio‐history of metrics also sheds light on transformations about relationships historically established between the welfare state and education that have shaped the representation of inequalities and social programs in education. The use of large‐scale surveys and controlled experiments in social and educational policies developed in the 1920s and 30s, even if their methods and techniques have become more sophisticated due to statistical progress. However, statistical reasoning is today no less persuasive in justifying the measurement of student skills and various forms of state intervention for “at‐risk” children and youth. With the rise of international organisations, notably the European Commission, demographic issues related to school population and the reduction of inequalities have shifted. It is less a question of selecting the most talented or gifted among working‐class students than of investing in human capital from early childhood to improve the education systems’ performance and competitiveness for the lifelong learning economy and European social investment strategy. This article attempts to illustrate this new arithmetic of inequalities in education at the European level.