This article analyses a case of action research collaboratively conducted by a university teacher and 50 students in a master's course in teacher training. Its originality resides in the socio-economic, academic, and conceptual nature of the obstacles encountered in the module; in the meta-theoretical orientation of the action research that was chosen to overcome them; and in how triangulation strategies were devised to compensate for the limitations imposed by the academic framing of the course. In spite of the brevity of the research cycle, both the structure of the course and teacher--student interaction improved rapidly and significantly, as did the latter's trust in the teacher. As a result, important advances in learning also ensued, and the pedagogical potential of this research method was thereby confirmed.