Aims: This paper was intended to explore the leadership practices of principals for knowledge management (KM) in the school context, and the influence of KM on the strategic planning (SP) capacity of school organizations to provide quality education for effectively coping with the challenges from education reforms. Methodology: A single-case study was conducted in a secondary school in Hong Kong. The school participated in a two-year QEF project for applying KM concepts and mechanism. In-depth interviews were conducted with the school principal, middle managers, and front-line teachers to investigate the leadership practices of the principal to implement KM in the school, and the influence of KM on the school's SP capacity for providing quality education. Results: Setting school direction for KM, developing teachers' skills and awareness for KM, creating supporting conditions and infrastructures for KM, aligning KM with the school's teaching and learning process, and building external coalitions for KM were found as the principal leadership practices for school KM. These practices could support the school in adopting the codification and personalization KM strategies and facilitate the acquisition, storage, and sharing of knowledge in the school. KM could help the school to effectively acquire, store, and share the knowledge for strategic analysis, choice, and implementation in the SP process, improving the school's SP capacity for providing quality education. Conclusion: Principal leadership has significant effect on the successful implementation of KM in the school context, which in turn plays an essential role on the school's SP capacity for providing quality education.