This article focuses on professional work placements for teachers of business and management. These one-year work placements seek to develop the teachers' knowledge of the business world, allowing them to improve their teaching practice and produce new pedagogical resources. We examine here, from the teachers' point of view, two questions: What are the particularities of the work placement as a context for learning (in terms of processes, roles and organisation, products)? What are the effects on their professional development? Two perspectives are articulated. On the one hand, a didactic perspective will examine the reconstruction of "business" as an object to be taught by the teachers. On the other hand, the professionalisation dynamics point of view will examine the shifts in teachers' perceptions.