© Young and MacPhail. This article presents case studies detailing the learning trajectories of two physical education (cooperating) teachers as they strive to establish and maintain their identity as competent and confident supervisors to pre-service teachers on school placement. The cooperating teachers who participated in the study share their experiences in attempting to construct a professional identity within the school placement triad. Lave and Wenger¿s (1991) theory of situated learning and the concept of legitimate peripheral participation were employed to investigate each of the cooperating teacher¿s journeys in their attempt to shape their professional identity through participation in a variety of professional learning communities. The data revealed that the cooperating teachers experienced various forms of legitimate peripheral participation and, as a result, their learning trajectories and attempts to construct professional identities were diverse. The cooperating teachers¿ learning did not always follow a positive trajectory, often meeting obstacles, resulting in the teachers experiencing both highs and lows during the supervision process.