This article describes a comprehensive strategy for developing a larger corps of effective principals, "The Principal Pipeline Initiative," launched by the Wallace Foundation in 2011. Its purpose is working to strengthen school leadership by documenting and evaluating leadership development in six urban districts (Charlotte-Mecklenburg Schools, North Carolina; Denver Public Schools, Colorado; Gwinnett County Public Schools, Georgia; Hillsborough County Public Schools, Florida; New York City Department of Education, New York; and Prince George's County Public Schools, Maryland.) Now two years into the initiative, decision makers are looking for evidence of what a strong pipeline looks like. An evaluation collected and reviewed qualitative data, including interviews with 113 administrators and surveys of novice principals and assistant principals. The survey also focused on preservice opportunities, support for novice leaders, and the role of partnerships in preparation and support. All six districts were building on strong preparation experiences in instructional leadership. All six districts in the Principal Pipeline Initiative put serious effort into forging university and organizational partnerships for their programs in leader preparation or novice support. Ongoing evaluations continue for the Principal Pipeline Initiative and, as districts head into the next school year, changes that foster success for student outcomes continue.