Purpose: This study aims to test the mediated effect of school climate in the relationship of principal time use (PTU) to student academic achievement using data from Singapore's 2011 Trends in International Mathematics and Science Study (TIMSS). Design/methodology/approach: Capitalizing on the large-scale data, the study examined how Singapore principals distributed their time across 13 leadership activities and tested using structural equation modeling (SEM) how Singapore principals' time use was related to student achievement through molding intermediate school conditions, such as school climate. Findings: The authors' findings suggest that Singaporean principals, when allocating time, generally emphasized (1) monitoring students' learning progress, (2) promoting school vision, (3) developing curricular goals and (4) monitoring teachers in areas related to curricular goals. Furthermore, after classifying the 13 principal activities into three broad domains, the authors find that Singaporean principals prioritize the domain of vision and goals over the other two domains -- facilitating teaching and learning through a safe, positive school environment and problem-solving with teachers, as well as self and organizational improvement. Finally, the authors' SEM manifested a partial mediated model, suggesting principals' strategic time use could serve as a malleable factor in yielding optimal student outcomes through developing a positive school climate. Originality/value: This study at present is one of the early attempts linking PTU, intermediate school conditions (e.g. school climate) and student outcomes using a mediated design and corresponding statistical modeling.