This case study reports on the experiences of teachers and student teachers during the process of developing and implementing professional development sites (PDSs) at one urban and two rural middle schools. The study examines the phases of development that teachers go through in the process of developing PDSs and how teachers' level of development affects the development of the overall PDS. It also examines the benefits, to student teachers and to supervising teachers, of PDS-based training of preservice teachers. The focus of PDS activity at the three sites was preservice teacher training. Student teachers at one of the PDSs responded positively to a 2-week orientation to the school, designed by a core group of teachers (n=6) at the site, which introduced preservice teachers (n=5) to teaming, the school advisement program, teaching strategies, management techniques, lesson planning, and media. Both student teachers and supervising teachers concurred on three primary benefits of the PDS program: (1) support was available for both preservice and cooperating teachers; (2) student teachers became familiar with the school and its procedures, which gave them a framework for understanding school operations and made the supervising teachers' jobs easier; and (3) student teachers had the chance to observe various teaching styles. (Contains 21 references.) (IAH)