Education research has established a significant relationship between school leadership and students' achievement. This study considers the leadership self-efficacy and practice of assistant principals (AP) in public schools in the domains of facilitating a supportive and collaborative learning environment, instructional leadership, school improvement, management, and family and community relations, as perceived by APs' self-reports. The findings of this study suggest that, in addition to APs' strengths in the domain of facilitating a collaborative learning environment and efficacy around family and community engagement, there were explicit gaps in the instructional leadership and school improvement practices of APs that need to be addressed. The study also confirmed that there continue to be a proliferation of duties and a lack of a consistent set of practices for APs.