This article synthesises some findings of an international research project called "Know&Pol" to question the effects of the OECD's Programme for International Student Assessment (PISA) on the public debate in three European countries (France, Portugal and Scotland). Using a political science approach, it shows that Pisa did not favour policy learning among actors, but confirmed their pre-existing opinions and policy stances and that it legitimised them by affixing them with the seal of a statistical international survey.