Despite the growth in research on the impact of school administration on educational improvement in the past 10 years, the characterization of the identity of school principals is a controversial, pending issue. In this study, we set out to undertake this characterization from a dialogic perspective by tracking four expert principals over the course of one academic year. Via a longitudinal design with multiple case studies, we analysed their repertoire of positions and their variations. The instruments included a reflective journal, interviews based on the self-confrontation method and a discussion group. Our results indicate not only that the principals share their positioning as promoters of learning and project managers when dealing with professional events but that dialogue among internal and external voices enables them to deal with the conflicts and tensions among positions constructively. We conclude that principals' professional identity can be developed through conscious, strategic reflection on the positions they take within the context of their professional activity. [Translation from Spanish by Mary Black.]