This article interrogates the legitimacy and influence of interest groups in the elaboration of two school reforms of the last stage of compulsory schooling in two Swiss cantons: Geneva and Vaud. Based on the principle of participatory democracy, the Swiss political system raises questions about the specificities of interest groups' influence on educational policies. What role is given to them by the political institutions? Conversely, what role do they grant themselves in school reform processes? This article is based on a sociology of public action and aims to determine whether interest groups influence educational policies. We investigated these actors' involvement in the development of the reforms through a thematic content analysis of four corpora of texts for each canton. Our analysis of the data indicates that the influence of interest groups operates on two fronts: agenda setting and implementation of reforms. In contrast, interest groups are little considered during the process of drawing up bills in Parliament.