This chapter highlights a process of creating, revising, and evaluating a professional development (PD) program for in-service upper elementary teachers (grades 3-6), titled the Central New Jersey Partnership to Enhance Mathematics Achievement (CNJ PEMA). Beginning with the research base that informed the initial design of the multi-year program, a description of the program components and implementation, a discussion of the revision process, and lessons learned from formal evaluation (daily feedback forms) and teacher reflections are provided. In particular, attention is focused on how the program sought to include teachers as partners in the creation and revision process as a way to provide them with a voice and choice in their own professional learning.