The paper examines the OECD's Programme for International Student Assessment (PISA), which has become a major component of OECD educational work. PISA measures the performance of educational systems through tests commissioned by the OECD. The paper discusses the OECD's role in the 'comparative turn' and describes PISA, its management, and effects. It provides examples of PISA's impact in Finland, Germany, and the UK, and examines its transnational effects on European policy actors. The paper concludes that PISA has become an influential tool for governing European education through numbers. PISA is conducted every three years and assesses 15-year-olds' knowledge and skills in compulsory education. It has a global reach, with 57 countries participating in the 2006 cycle. PISA focuses on practical application of skills in everyday life rather than school curriculum mastery. It has become a key indicator of educational policy success, influencing national and international education systems. In Finland, PISA results led to a re-evaluation of the education system, with a focus on teacher autonomy and comprehensive schooling. In Germany, PISA results prompted urgent educational reforms, including the development of new standards for student competencies. In the UK, PISA results were well-received, but there was no significant policy change. The UK's response was more cautious, with a focus on maintaining high-stakes testing and data production. At the European level, PISA data are used to inform policy decisions and promote evidence-based policy-making. The European Commission relies on PISA data for its education policies, and there is a growing emphasis on using PISA as a tool for international comparisons. However, there is also a recognition of the limitations of PISA data and the need for a balanced approach to using international assessments. The paper argues that PISA has become a significant governing resource for Europe, influencing education policy at both national and transnational levels. It highlights the role of PISA in shaping educational priorities and promoting a focus on lifelong learning and applied skills. The paper concludes that PISA is a powerful political technology that shapes education policy and governance in Europe.The paper examines the OECD's Programme for International Student Assessment (PISA), which has become a major component of OECD educational work. PISA measures the performance of educational systems through tests commissioned by the OECD. The paper discusses the OECD's role in the 'comparative turn' and describes PISA, its management, and effects. It provides examples of PISA's impact in Finland, Germany, and the UK, and examines its transnational effects on European policy actors. The paper concludes that PISA has become an influential tool for governing European education through numbers. PISA is conducted every three years and assesses 15-year-olds' knowledge and skills in compulsory education. It has a global reach, with 57 countries participating in the 2006 cycle. PISA focuses on practical application of skills in everyday life rather than school curriculum mastery. It has become a key indicator of educational policy success, influencing national and international education systems. In Finland, PISA results led to a re-evaluation of the education system, with a focus on teacher autonomy and comprehensive schooling. In Germany, PISA results prompted urgent educational reforms, including the development of new standards for student competencies. In the UK, PISA results were well-received, but there was no significant policy change. The UK's response was more cautious, with a focus on maintaining high-stakes testing and data production. At the European level, PISA data are used to inform policy decisions and promote evidence-based policy-making. The European Commission relies on PISA data for its education policies, and there is a growing emphasis on using PISA as a tool for international comparisons. However, there is also a recognition of the limitations of PISA data and the need for a balanced approach to using international assessments. The paper argues that PISA has become a significant governing resource for Europe, influencing education policy at both national and transnational levels. It highlights the role of PISA in shaping educational priorities and promoting a focus on lifelong learning and applied skills. The paper concludes that PISA is a powerful political technology that shapes education policy and governance in Europe.