Although schools have the primary responsibility for educating children and adolescents, schools alone cannot prevent the use of tobacco, alcohol, and other drugs. Preventing youth from smoking, drinking, and using drugs must be a collaborative effort, jointly undertaken by the school, community, and youths themselves. This guide was developed to explain the partnerships that schools and communities can create to share the responsibilities of planning, funding, and implementing preventive strategies and programs. The first section presents a conceptual framework for planning by reviewing the extent of the substance abuse problem among youth, identifying misconceptions that lead to ineffective programs, defining drug use as a behavioral problem determined by many systems of influence, exploring the need for an integrated approach to prevention, identifying both risk and protective factors within students' influence groups, formulating a new definition of prevention, and introducing a comprehensive health approach to drug prevention. The next section develops a leadership role for schools, explaining how to build a partnership among schools, law enforcement, and the community; identifying the planning steps; recommending a comprehensive program for the school site; considering community- and school-based program strategies; and listing criteria for preventive programs and curricula. The final three sections of the guide look briefly at the intervention plan, school policy, and program support. Relevant sections of California legal codes, resources, and references are appended. (NB)