With the rise of polarization and extremism, the question of how best to transmit civic virtues across generations is more acute than ever. In this paper, we test the hypothesis that schools can be the place for this transmission by empowering students and gathering them around concrete and democratically chosen objectives. We draw on an RCT implemented in a large sample of middle schools in three European countries. The evaluated program leads students to carry out collective citizenship projects in their immediate communities under the supervision of teachers trained in student-centered teaching methods. The program significantly increases student altruism, their political self-efficacy as well as the quality of their relationship with their classmates and their respect for the rules of school life (less sanctions and absenteeism). In all three countries, the benefits are greater for students with the highest level of altruism and interest in politics at baseline. Investments made at an early age appear to be complement to those made during adolescence for the production of civic virtues.