This article draws on data from an action research project carried out in a lower secondary school environment in the Czech Republic. The project involved the implementation of a teacher professional development programme aimed at transforming teacher-student communication and reinforcing opportunities for student participation in classroom discourse. This article presents a description of a case study of transformation, in which a female teacher implemented triadic interaction, a communication structure in which students respond to each other immediately. The discussion shows that the processes involved in implementing triadic interaction in a classroom are not straightforward and entail overcoming certain dilemmas and harmonizing the teacher's personal goals with goals set by the researchers. It also reveals that the process of transformation may cause temporary emotional distress in teachers as they abandon their habitual methods but that emotional tensions and dilemmas can be overcome by reflective discussion between teachers and researchers.