Purpose: In professional learning communities (PLCs), teachers collaborate and learn with the aim of improving students' learning. The aim of this study is to gain insight into teachers' perceptions of their schools' changing toward PLCs and conditions which support or hamper this change. Design/methodology/approach: Questionnaires were completed by a total of 2.111 teachers from 15 Dutch secondary schools for three years. With the use of multilevel regression analyses, the research questions were answered. Findings: Although the development of a school toward a PLC seems to be a slow process, the findings demonstrate the influence of school conditions on this development. Human resource management (HRM) stands out, as this school condition has a direct and longitudinal effect on the change. Practical implications: The main recommendation is to embed PLC elements in HRM policies such as facilitating teachers to collaboratively work and learn and aligning teachers' professional development with schools' vision and ambitions. Originality/value: PLCs have been studied occasionally in longitudinal in-depth case studies or in large-scale, cross-sectional research. This large-scale longitudinal study provides insights into the sustainability of schools as PLCs and the school conditions that are associated with sustainability.