Drawing on archival sources, interviews, and research literature, this article offers new insights into the making, structure and long-term effects of the International Educational Indicators (INES) programme of the Organisation for Economic Co-operation and Development (OECD). The article argues that INES was crucial in setting the OECD on the path to becoming a global education policy actor. Although science has informed policy making for centuries, the 1980s mark the start of a much closer imbrication of evidence-making for policy. By focusing on those renewed encounters of education science with policy-making, the article examines the INES indicators as a boundary infrastructure. It shows the ways that INES materialised many of the OECD ambitions at the time. In other words, through INES, the OECD gained the unique confidence, expertise, and reputation in the field to deliver large international comparative works on a global scale.