According to the literature and to international politics, contemporary societies should learn how to respond immediately to crises in the environment, the economy, in health etc., as well as to the rapid socio-economic, demographic and technological developments on a global level. Education has been placed at the center of this effort and teachers are at the forefront. Within this context, educational administration promotes teachers' lifelong Professional Development (PD), the transformation of school units into Professional Learning Communities (PLCs) and the strengthening of school principals' capacity for pedagogical leadership. The Greek educational policy and school administration, having been formulated by long-standing and deep-rooted centralized and bureaucratic procedures, has recently begun a systematic effort to respond to the above international calls without much success. Therefore, this study aims to investigate the extent to which efforts for Greek schools to become learning communities that support teachers' lifelong PD have been successful and how teachers, as recipients of these changes, perceive them. The research results mainly showed that schools function to a moderate degree as PLCs while school principals have moderately developed the appropriate leadership practices which would support teachers' PD through PLCs. The findings of the study highlight the importance of the collaborative, supportive and pedagogical role of school principals, as well as the need for reforms (e.g. in the design and implementation of the school curriculum and school staffing strategy) and for establishing support for learning networks in schools.