Moral education and moral growth are very important topics, and have been so as much in the fields of moral psychology and moral education as in the policies of governments and international institutions over the past decades. These two topics are also central themes within the educational proposal of Philosophy for Children (P4C), as seen in theoretical reflection and in educational research. It is necessary to start from a more global approach to moral growth, focused on the development of capacities. Such abilities are to be understood as virtues or personality traits that enable us to achieve a full life, that is, to become good people. The transformation of classrooms into communities of philosophical inquiry, following the educational guidelines of P4C, can contribute to the achievement of this objective. Here we present the psychological and methodological underpinnings of an educational research project that we are applying to a small sample that includes two groups—experimental and control—in a typical classroom environment. We are administering tests at the beginning and the end of the application of a moral education model according to the basic principles of Philosophy for Children. The objective is to verify that our research design could be used to evaluate the contribution of this educational model to the students’ moral growth, understood as the consolidation of the students’ moral habits and competences.