As a result of the emphasis on professional development schools (PDSs) in teacher education over the past decade, numerous theoretical articles, process descriptions, and research reports provide considerable information about the nature and impact of school-university partnerships (Abdal-Haaq, 1998; Book, 1996). Several articles outline the perceived benefits for school and university faculty of participation in joint inquiry (e.g., Darling-Hammond, 1992). The literature provides particular insights into what happens to teachers, future teachers, and to a lesser extent, university professors; and how schools and universities change as a result of their collaboration. Most studies focus on roles and relationships, teacher attitudes, and teacher education, rather than on the elementary and secondary students in PDSs (Book, 1996). Although almost all PDS partnership goals include a stated emphasis on improved school achievement and student learning (Freeman, 1996), few studies address the impact of PDS efforts on student outcomes (Abdal-Haqq, 1998; Book, 1996; Valli, Cooper, & Frankes, 1997). Why have researchers not adequately addressed the impact of PDS on K-12 student outcomes? Field research that assesses student learning is difficult and fraught with pitfalls that threaten its rigor. Easy-to-obtain measures such as standardized tests may be too far removed from the focus and activities of PDSs to provide adequate measurement of impact on student learning. Reform efforts focusing on restructuring typically seek to evaluate authentic student activities that have relevance and meaning for them (Newmann, 1991) but may be difficult to measure. Furthermore, it is difficult to isolate distinct variables in complex interventions such as PDSs that can be directly related to student outcomes. Use of control group or other traditional experimental designs, which might serve to identify cause-and-effect relationships, may be seen as unethical by teachers and administrators because they deny potentially beneficial treatments from groups of students and teachers in the school. Another possible reason for the paucity of research on the effects of PDSs on K-12 students involves issues of trust and collaboration between practitioners and researchers. Many opportunities for inquiry to be misunderstood exist in partnerships where tenuous relationships are evolving between two very different cultures struggling with issues of trust, power, and control (Knight, Wiseman, & Smith, 1992; Ruscoe, Whitford, Egginton, & Esselman, 1989). Teachers may have concerns about the implications of experimentation in their classes because the experience may be damaging to students (Darling Hammond, 1992). Furthermore, partnership research can directly affect the professional lives of teachers and administrators. For example, teachers may see research as competing with instructional goals (Book, 1996); less than outstanding findings may reflect badly on programs, teachers, and administrators increasingly under public scrutiny. Teachers and administrators have traditionally been the objects of study by university researchers who may or may not even share their findings with the objects of their research. Teachers often see little relevance in studies that answer questions they do not ask and reports that use terminology they do not understand. As a result, the gap between research and practice widens. One response to the problems of mediating research and practice and excluding teachers' voices in the development of knowledge about teaching and learning is the collaboration of school and university researchers in determining PDS impact. Collaborative inquiry (Sirotnik 1988), also known as teacher research (Hollingsworth & Sockett, 1994), action research (Oja & Pine, 1987; Reason 1994), or collaborative research (Lee, 1993), holds significant promise. The goal of collaborative teacher research is to link research with practice to affect teacher thinking and instructional behavior, school systems and culture, and student outcomes. …