Increasingly, educational reform is linked to the concept of professional learning communities (PLCs). Definitions of PLCs vary, but generally the concept refers to a group of educators who "continuously seek and share learning, and act on their learning" (Hord 1997, 6). Stoll and her colleagues, concluding their review of the current state of PLCs and research, observe that there is a "paucity of longitudinal research" and that "little is yet known about the potential for establishing enduringly effective PLCs." The concept, they conclude, is new, and much work is needed to develop and then test its potential. As researchers study PLCs to gain greater insight into their problems and possibilities, this article recalls an often-forgotten and consistently misrepresented moment in the history of American education, the Eight-Year Study, during which such communities formed and flourished. Five lessons of importance to school reform emerge from this inquiry into the Eight-Year Study and PLCs: (1) School reform consists of teacher education and capacity building; (2) Powerful teacher education is more than a matter of learning about and practicing promising teaching techniques, it involves engagement in exploring, with others, pressing personal and professional problems and issues--the sorts of issues that now form the focus of the teacher-researcher movement; (3) Sustained school reform will require both a foundation of trust among teachers and life-enhancing relationships with one another and with young people; (4) Powerful teacher education requires that schools, colleges, and universities join in a mutual quest for change and improvement; and (5) The story of the Eight-Year Study is one of uncertain but thoughtful educational experimentation, of testing ideas, of gathering data, and of remaining open to contrary evidence in the hope and the belief that interesting, if inevitably temporary, solutions would be found to situation-specific problems.