This article presents a few results of a study on the professional identity of high school teachers in Belgium’s French community. This study shows that teacher identity is a collective, contextual and singular construction. The teachers seem to have partly common backgrounds and visions of the profession, but how they experience and perceive it varies greatly from school to school, and professional identity seems to be built first and foremost on student-related contingencies. However, this identity construction also stems from the specific history of each teacher, their personal motivations, and each individual’s way of adapting to teaching conditions. In particular, the study shows that the professional identity of teachers is strongly structured by a tension between their ideal concept of the « real work » and the « dirty work » they sometimes have to do, especially in more difficult establishments. This tension can be understood both in relation to the personal stories of each teacher and specific employment conditions, and in terms of a larger educational and institutional context.