This paper reviews the research work we have been conducting within a project on "Social Participation and Regulation in Educational Policies". In today's societies within advanced democracies, we identify a trend towards the regulation of educational systems based on decentralisation processes, increasing autonomy of schools and increasing participation of educational actors (teachers, parents, local actors, students in the case of secondary schools, other professionals in schools,...). In the last 15 years, several legislative acts have given a contribution to reinforce this trend.Within this context, the particular focus of the paper is centred on the idea of "social participation" that has a central role in this changing process of regulation of educational administration. Following a previous work in which we intended to build an operational concept of social participation, this paper puts forward some results of the research work we have been doing recently.How do educational actors participate in the school organisation? What are the conditions that make it easier to participate? What are the obstacles which prevent active participation? What are the effects of this participation? Which actors are more participative within the school organisation? These are some questions which framed our research both on the theoretical and empirical domains. The paper draws on data taken out from an empirical research. Using a case study methodology, 3 schools were selected to deepen the understanding of the idea of social participation. These schools are located in the suburbs of Lisbon and belong to different times and phases of the educational system development: in the 60's/70's when an enormous growing in the number of students was experienced; in the decade of 80 when this trend was less evident; in the 90's which represents the beginning of the schools' autonomy. Data collection combined a variety of sources: school document analysis, official legislation, questionnaires and written records of meetings of school boards. Within these case studies we identify some contributions to explore and clarify the questions mentioned above.The paper also draws on analytical research of theoretical contributions taken out from several disciplines, since we intend to build a multidisciplinary frame to deepen the understanding of the idea of social participation within today's societies in Europe.