In recent years, professional development for public school educators has come to be seen as a key component of school improvement plans, particularly large-scale systemic change programs. This Digest outlines what research and best practice suggest about effective professional development for elementary and secondary teachers working in restructured, learner-centered schools. It considers the implications of traditional school scheduling patterns for implementing effective professional development and shares some approaches that various schools and districts have taken to finding time for teacher development activities. An effective professional development program provides adequate time for teachers to acquire, practice, and reflect on new concepts and skills, as well as time to collaborate and interact with peers. In traditional school schedules, sufficient time for this kind of teacher activity is not normally integrated into the school day. Schools and school districts have devised several approaches and strategies to making time for teacher development available during school hours. Restructuring the school day or school year, as well as other approaches to incorporating teacher development into regular school schedules, may provoke opposition from parents, financial managers, and community interests. (IAH)