This study critically examines the persistent fragmentation in the implementation of Education for Sustainable Development and advances a rethinking perspective on how sustainable education systems can be achieved through greater integration. Despite the growing global emphasis on sustainability, many educational institutions continue to adopt programmatic and isolated approaches, resulting in limited systemic impact. Addressing this gap, the study investigates how strategic leadership and institutional innovation can be reconceptualized to support the transition from fragmentation to integration.

Using a qualitative embedded case study design, this research draws on secondary data and employs thematic analysis combined with PESTEL Analysis to examine both internal institutional dynamics and external environmental influences. The findings reveal that institutions operate within a transitional sustainability model, characterized by incremental innovation, adaptive yet centralized leadership, and fragmented sustainability practices. This condition reflects a broader structural misalignment between sustainability goals and institutional capabilities.

The study argues that achieving sustainable education systems requires a fundamental shift from fragmented interventions toward systemic integration, where leadership and innovation are not treated as separate dimensions but as mutually reinforcing processes. In this context, strategic leadership must evolve into a more systemic and participatory form, while institutional innovation must be embedded, coordinated, and aligned with long-term sustainability objectives.

A key contribution of this research lies in rethinking the relationship between leadership and innovation as an integrated nexus that drives sustainability transformation within dynamic environmental contexts. By emphasizing the transition from fragmentation to integration, this study offers a novel conceptual framework for understanding and advancing sustainable education systems. The findings provide important implications for theory, practice, and policy, particularly in developing and resource-constrained contexts.

Keywords: Sustainable Education Systems, Education for Sustainable Development (ESD), Strategic Leadership, Institutional Innovation, Sustainability Transition, Systemic Integration.