The theoretical field that we chose to get a better understanding of the real work of the teachers is the field of work psychology – and within that field, the framework of « Clinic of Activity », which is at the same time action and research on the processes of development of human activity. Our methodology implies the construction of dialogical frames, enabling the professionals to develop a new activity on their past activities. In this dialogical activity the professionals may find resources to develop their own power to act on their professional situation. This dialogical activity reveals the psychological instruments of the development of the activity and its factors of encystment.