Research in general education has demonstrated that school principals have a substantial impact on the effectiveness of schools and related student achievement. This is not a direct impact, but rather relates to how principals indirectly impact student learning by improving the learning environment of a school and the practice of teachers. More specifically, the dimensions of principal practice that are most influential in improving schools and student achievement relate to establishing a shared vision, facilitating a high-quality learning environment for students, building the professional capacity of teachers, creating a supportive organization for learning, and connecting with external partners. Only in recent years has research begun to emerge related to the role of the principal in supporting improved achievement for students with disabilities in schools that are effective and inclusive. In this chapter, we review research related to what principals can do to facilitate the development of inclusive schools that are also effective in improving achievement for students with disabilities and other students who struggle to learn. After reviewing these dimensions of principal practice, we then provide a brief case study that illustrates how a principal in an effective inclusive school applied several of these practices, including staff collaboration, progress monitoring, and professional development to improve teacher practice and student outcomes. [For the complete volume, "General and Special Education Inclusion in an Age of Change: Roles of Professionals Involved. Advances in Special Education. Volume 3," see ED605014.]