In this article, we examine the problems inherent in the relationships between teachers’ reflective activity with regard to their own work, the production of knowledge about teaching, and transformations in their subjectivity. Our analysis is based on systematic exchanges around pedagogical questions in a group of teachers and researchers in mathematics education during a collaborative work. The close examination of students’ productions within a framework of critical analysis of teaching was a major event for the teachers, as they reinterpreted the students’ relationships to knowledge. This analytical work modified teachers’ self-perceptions with regard to their potential to engage in intellectual production based on reflection about their own professional activity. The collaborative work allowed them to imagine new solutions to the problems posed by their teaching practice. It is in this creative possibility that the transformation of subjectivity lies.