This paper attempts to identify leadership practices and qualities of school teachers as they engaged in effecting change initiated by a curriculum reform in Hong Kong. Based on interview data of teachers from nine schools, this paper shows how teacher leadership manifested itself in schools. Three approaches to teacher leadership were identified, each delineating how teacher leaders approached the implementation task--as a compliance exercise, an adaptive exercise, or as a capacity building exercise. This paper confirms that different levels of teacher-leader engagement in professional enquiries constitute different teacher leadership practices, which have differential impacts on teaching and learning practices and the effectiveness of school improvement efforts. Implications for developing teacher leadership in schools are discussed.