Purpose: The purpose of this paper is to examine the effects of different dimensions of instructional leadership on student learning in Hong Kong secondary schools, whose broader institutional contexts are critically characterized by high accountability policy environments. Design/methodology/approach: This study utilizes standardized test scores collected from (n = 2,037) students in 42 secondary schools and data collected from key staff's perceptions of leadership practices, to investigate two dimensions of instructional leadership, which are conceptually interdependent but distinctive--i.e. instructional management and direct supervision of instruction. A cross-level interaction analysis of hierarchical linear modeling was employed to investigate the effects of the two dimensions of instructional leadership on student learning. Findings: Leadership practices focused on instructional management were found to enhance student learning by boosting the positive effect of students' attachment to their school on academic achievement. In contrast, leadership practices related to direct supervision of instruction were found to undermine student learning by weakening the positive effect of student perceptions of school attachment on academic performance when other school- and student-level characteristics are held constant. Originality/value: The paper reveals the contrasting effects of instructional leadership as a multi-dimensional construct which is central in the current education reform agenda, rooted in accountability-oriented policy of Hong Kong. It draws a number of implications for principal instructional leadership in Hong Kong Schools as they deal with demands for external accountability. (Contains 4 tables, 1 figure and 16 notes.)