Group investigation is an organizational approach that allows a class to work actively and collaboratively in small groups and enables students to take an active role in determining their own learning goals and processes. As part of reform and restructuring efforts, Beaverton High School (Oregon) implemented the Group Investigation model with sophomores, in 1990-1991, in a 6-week unit on the Gulf War. This unit was taught by four English and four social studies teachers in seven classes. The unit had six stages: organization of research groups, planning the investigation, student investigation and research papers, preparing the report by study teams, the final presentation, and testing and evaluation. After this initial experience with group investigation, the faculty made such a unit a standard part of the sophomore interdisciplinary curriculum. The Group Investigation method was modified over time until, in January 1994, the most ambitious teaching configuration was tried: biology, English, and government teachers offered a 3-course block. Both students and teachers rated the unit positively. The significant difficulty with this unit had to do with the school's science program which was tracked into biology (low) and chemistry (high) strands. The resulting lack of heterogeneity meant that students often lacked role models for behavior, academic achievement, and leadership. Reflection on past experience led the faculty to continue use of group investigation as an organizational principle and to use problem-based learning as a tool to focus selection of topics, structure a richer learning situation, and refine assessment methods. A key finding was the congruence between the social organization of the classroom and the governance of the school. (LL)