Although the value of school-community partnerships is unquestioned, the reasons for success and failure are not sufficiently understood. This mixed-methods case study examines 60 years of partnering at one urban high school, using Bronfenbrenner's ecological systems theory to better understand the effect on student development as measured by variables such as graduation, attendance, and drop-out rates. Successful partners achieve "cultural cohesion" by building collaborative relationships that encircled students, whereas failed partnerships ignore ecological theory. In contrast to conventional reform strategies that focus on curriculum and/or school structure, the author offers a cultural reform strategy that emphasizes relationships. (Contains 2 figures and 9 notes.)