This article aims to examine the predictive relationships of self-evaluation capacity and staff competency on the effect of strategic planning in aided secondary schools in Hong Kong. A quantitative questionnaire survey was compiled to collect data from principals of the participating schools. Confirmatory factor analysis and reliability tests were applied to confirm the constructed validity and reliability of the survey instrument. Multiple regression analysis was applied to explore the relationships among variables. The capacity of self-evaluation mechanisms and staff competency are identified as predictive factors for effective strategic planning. An effective quality assurance (QA) mechanism could support the sustainable development of school organization. School administrators could embed self-evaluation mechanisms into strategic planning and provide staff development to improve the QA systems in their schools.