This research examines how students, from a public high school of Rio de Janeiro, discuss and resolve moral dilemmas involving issues of justice, human dignity and practices of discrimination and prejudice on the basis of gender differences, ethnicity and sexual orientation, having as theoretical background both the discourse’s ethics (Jürgen Habermas) and the theory of moral development (Lawrence Kohlberg). The moral dilemmas were applied and analyzed using the methodology of focal groups. This work was motivated by the finding of many conflicting relationships in school life, caused largely by lack of recognition and respect for interpersonal differences as well as because of the limits on teacher training to deal with these conflicts. The study aimed to characterize the moral dilemmas and investigate the learning process of attitudes and values from the selected theoretical framework, focusing on issues related to diversity in school life. This research is bound to an institutional research project entitled Cultural Diversity, Educational Practice and Ethical Minimum (2008- 2010), which is being developed by the research line Ethics and Intercultural Pedagogical Practice, from the Study Group on Everyday Life, Education and Cultures (GECEC), at the Graduate Program in Education at PUC-Rio.