As the principal of Baruch College Campus High School in New York City, the author wanted to help her teachers communicate with one another and put structures in place to develop the vision of the school while giving teachers opportunities for input and growth. After conducting a needs assessment, she found that teachers who had an ally in the building learned a lot from informal conversations with one another. In addition, she learned that the best professional development happened when teachers had well-structured time to meet and reflect on their practices, such as in grade-based or departmental teams. She used these findings to develop the Teacher Collaboration Model (TCM) and a grant program that encourages teachers to collaborate to develop professionally. The goal of TCM is that everyone in the school collaborates--students, teachers, parents, and administrators. Almost every teacher has a collaborative partner, and teachers meet weekly to plan curricula, make decisions, and agree on common benchmarks for their classes. This practice prompts teacher dialogue about the thinking behind their planning and helps teachers reflect on their practice.