In discussions on the contribution of leadership in improving schools, transformational leadership and instructional leadership are, more often than not, portrayed as disparate practices. The former argues for developing teacher collaborative capacity in schools, whereas the latter advocates establishing controlling measures on teaching quality; both lines of thought attract their own supporters. The recent finding that instructional leadership practices have a greater impact on student learning has apparently marginalised researchers' attention paid to transformational leadership. This study argues that both leadership practices are important to student performance; transformational leadership can foster a trusting environment in schools for facilitating the effective enactment of instructional leadership. Based on a dataset on Hong Kong vice-principals, this quantitative study found that the widely recognised link between instructional leadership and student outcomes did not hold in low-trust schools. As transformational leadership was conducive for trust building, its role in shaping student performance should be re-addressed.