Professional development provides a means to build capacity among school personnel when it is delivered as part of a systematic, long-term approach to school and teacher improvement. This research examines a sustained, diocesan-wide professional development model, called the ACE Collaborative for Academic Excellence, that aims to build capacity for school improvement. It utilizes a framework modeled on the pillars of the Alliance for Catholic Education that targets three areas: teacher, group, and vision capacity. An analysis of participant survey data probes the extent to which teacher, group, and vision capacity are enhanced in this model and suggests several ways this professional development model and others can be strengthened to effect lasting change in Catholic schools. (Contains 1 chart and 5 tables.)