School-external expectations regarding implementation of reforms and innovations often do not lead to successful school improvement processes in schools. To better understand these processes in schools, this paper aims to investigate school improvement processes on a deep level by focusing on cognitive, metacognitive, and motivational regulation strategies used by school teams and by exploring what school-external and school-internal factors are related to this strategy use. Principals, teachers, and specialist teachers (N = 1328) at 59 primary schools responded to an online questionnaire indicating their school's use of regulation strategies on school improvement. Results from descriptive, variance, and hierarchical multiple regression analyses revealed that school teams use all forms of school-based regulation strategies but that schools differ significantly in their strategy use. These differences were mainly explained more by school-internal deeper structures (e.g., task cohesion) and less by school-internal surface structures (e.g., school size) and not at all by school-external factors (e.g., governance systems).