This paper provides an analysis of the implementation and the outcomes of Scienza Attiva, an Italian national project for secondary school students, that makes use of deliberative democracy tools to address socio-scientific issues of great impact. The analysis has required a mixed method including surveys of students' pre- and post-project opinions, focus groups and interviews with students and teachers. The results from this evaluation study provide evidence that the project improves students' understanding of socio-scientific issues, strengthens their awareness of the importance of discussion and positively influences interactions in the classroom.