How do school principals work in France? What challenges do they face in their daily professional lives? What is their relationship with school development? What can we learn from this for our own context? Pierre Tulowitzki addresses these questions in his study. He examines how school principals spend their working hours, when and how they engage with school development, and what phenomena manifest in this context. The study is based on case studies from five secondary schools (collèges) in a school district near Paris.