This research focuses on the differentiation of a beginner physical education and sports teacher (PSE) exercising in priority education. It is part of a comparative approach to didactics, enriched by the theoretical and methodological foundations of the clinic ofactivity. We seek to understand how beginner teachers can reconcile the various constraints on their activity, particularly those relating to the characteristics of the context, to their motives for action and institutional requirements, to lead and differentiate their teaching. The results show that the creation of conditions conducive to work is made possible through flexible management of the didactic environment and the construction of various communication structures centered on learning. Differentiation results from multiple dilemmas such as managing the class, conducting lessons for the benefit of each and every student, promoting tactical or technical knowledge and respecting/adapting prescriptions. Beyond this, we discuss perspectives for developing the power to act of beginner teachers exercising in a difficult environment.