This project, entitled B-FREE, was designed to develop personal and social skills in adolescents deprived of their liberty. The aim was to facilitate future social inclusion by transforming the participants' behaviour and self-responsibility for their actions, through Physical Education classes based on Hellison's Teaching Personal and Social Responsibility Model. We used a qualitative methodology under a constructivist philosophical worldview and an ethnography research design. Data was collected through observation records, adolescents self-assessment and key actors' observations. The results revealed evident improvements in the behaviours and attitudes of the adolescents, both in the Physical Education class and in their daily lives, confirming the adequacy and effectiveness of that teaching model to improve the detained adolescents' behaviours, through physical education.