Findings from research studies suggest that school leadership accounts for fully one quarter of total school effects on pupils, making it second only to classroom instruction among school-based factors affecting student achievement (Leithwood, Louis, Anderson & Wahlstrom, 2004). While a considerable body of research has analyzed effective school leadership in general, remarkably few studies have examined the leadership of middle grades schools in particular (Anfara, Roney, Smarkola, DuCette, & Gross, 2006), despite the fact that students' performance in the middle grades has been linked to later life success (Balfanz, 2007). The purpose of this study was to describe and analyze middle grades principals' perceptions of effective school leadership. We focus within this article on leadership dispositions in particular, in the interest of space and because the domain remains particularly unexamined within the middle grades literature. We begin with a brief overview of related research and the theoretical framework that grounds our study. We then describe the qualitative methodology employed to pursue our purpose. Next we examine two key areas of our findings on middle grades leadership dispositions: developmental responsiveness and relationship. Finally, we consider the implications of this work for policy, practice and future research.