In this article, the author explores the promising practices of Audrey Union (all names in this article are pseudonyms), a white principal of Integration Middle School (IMS), which served nearly 400 students in sixth through ninth grades. Approximately 40% of the students were of color and a similar percentage qualified for free and reduced lunch. In particular, the author examines Audrey's influence in creating systemic, sustained, and differentiated professional development for social justice in her school. This is a critical case study in that her practices offer in-depth insights for addressing at least two crucial challenges faced by middle level principals. The first challenge concerns providing quality professional development opportunities for "all" teachers to enhance their practice for "all" students, a core component of school improvement. Several authors have provided models of or demonstrated the crucial role principals play in creating these opportunities. However, documented principal practice is needed for creating a more comprehensive understanding of how they differentiate professional learning for individual teaching needs, especially considering the next challenge. A second, related challenge, despite its importance, has received much less attention. It is also the challenge that set Principal Union apart from most principals: providing professional development that encourages teachers to prepare students as citizens who understand and address community, national, and global social issues. In other words, Principal Union's practices not only demonstrated commitment to professional development for equity and academic excellence, but also commitment to professional development driven by student learning for diversity and social action.