This study advances understanding of leadership for school improvement by reframing collaborative leadership as a relational organisational process rather than as a structural distribution of roles. While prior research has emphasised shared and distributed leadership, limited attention has been given to how leadership is enacted through everyday interaction, particularly within highly centralised educational systems. Adopting a social constructivist perspective, the study employs an interpretivist qualitative multiple-case design across 18 primary schools in Cyprus, drawing on data from 108 participants, including principals, middle leaders, and teachers. Data were generated through semi-structured interviews and document analysis and analysed using thematic analysis. The findings show that collaborative leadership operates through three interrelated relational mechanisms: participatory engagement, relational interaction, and collective sensemaking and problem-solving. These mechanisms enable the mobilisation of professional knowledge, foster trust, and support coordinated action, thereby strengthening organisational capacity for improvement. The study contributes by reconceptualising collaborative leadership as a relational organisational mechanism, providing empirical insight into how leadership is enacted through interaction, and demonstrating how such practices function as a situated response to constrained agency in centralised systems. Overall, it offers a practice-based account of leadership as a relational organisational accomplishment beyond the principal.
