This paper describes a professional development model, which emerged from two projects, that had professional development of teachers as an important component. The first project, Project Lighthouse, was designed to facilitate the inclusion of students with disabilities into general education classrooms. In this project, faculty and staff determined what kind of professional development they needed and in what format, and then school-based teams planned specific activities to address their identified needs. The second project was a science project designed to equip teachers with the knowledge and skills to help their students succeed in the sciences. The project included a summer institute, Saturday sessions during the school year, and a site visit from the project facilitator. Based on experiences with the two projects, researchers created a professional development model that facilitates the growth of teachers toward sustained skill mastery using a focused, programmed approach which provides support to the teacher at each of six stages (basic information, observation, guided practice, skill enhancement, initial mastery, and sustained mastery levels). (Contains 16 references.) (SM)