This study explores the factors that contribute to teacher learning within a one-year systems-thinking-based professional development (PD) programme at a private school in South Africa implementing systemic problem-based learning (PBL). Employing Q methodology, the perspectives of 31 teachers were analysed, resulting in six distinct collective viewpoints that illustrate the interplay of three nested systems: the individual teacher, the learning activity system, and the broader school context. The six factors identified were: (1) Teachers taking responsibility for their own learning; (2) How PD shall be organised - (2a) Strong school-level support and parental communication to improve student outcomes; (2b) Promoting a more agentic approach to learning; (3) Multiple PD - USEFUL or not? (3a) Multiple PD opportunities to improve student outcomes; (3b) Valuing feedback as part of PD; and (4) The school’s overall encouragement of student-centred learning. These diverse perspectives reveal complexity, diversity, and unpredictability of teacher learning, shaped by individual characteristics, collaborative practice, and institutional support. This study further extends the conceptualisation of teacher learning as a complex dynamic system by examining the interplay among three nested systems: the individual teacher, the learning activity system, and the broader school-level system underscoring the importance of practice-based engagement in helping teachers deepen their understanding of the pedagogical principles underpinning their work to improve classroom practice.