This article addresses the policy implications of participation in international large-scale assessments (ILSAs), particularly the Programme for International Student Assessment (PISA), and the ways in which such implications might influence mathematics education. Taking Norway as a special case, this discussion focuses on insights into teaching, learning and assessment practices that can be inferred from the PISA study, and how participation in ILSAs has contributed to educational policy and even changed policymakers' perspectives on schools, teachers and students. Following publication of the PISA 2000 results, Norway experienced a 'PISA shock', leading to the implementation of a national quality assessment system and national tests. In addition, changes were made to the mathematics curriculum for compulsory school and to mathematics teacher education. More recently, public debate has focused less on rank and league tables, shifting instead to the high number of low-achieving students and the low number of high achievers. Moreover, there has been little uptake of policy advice provided by the Organisation for Economic Co-operation and Development (OECD), which focuses on strengthening accountability measures. Furthermore, although the Norwegian educational system in the past decade has undergone a decentralisation process, the educational system still follows the Nordic model, which focuses on equity and 'education for all.' Analyses of the Norwegian case indicate that policymaking takes place in highly cultural contexts, and that international studies might be used merely to validate existing policy directions.