This paper advocates the importance of sex and relationships education in the context ofeducation for democratic citizenship and human rights. To this end, educational action research is proposed as a methodology appropriate to give a voice and encourage the active participation of the subjects, and to promote, thereby, processes of social change towards democratic citizenship, which focuses, here, on sexual and gender equality. The paper reports on the contributions of sex and relationships education values to democratic citizenship, as well as the social value of educating adolescent sexual and affective relations. In so doing, the social class perspective is emphasised. The paper concludes defending the need to invest on education for democratic citizenship that includes sex and relationships education.