This paper discusses ways that educators can develop a variety of school-based programs that can significantly reduce the threat of serious violence and disruptions. An effective technology of school safety, it states, begins with knowledge and understanding. The purpose of the paper is to outline the current state of knowledge about school-violence prevention. It looks at how data about school violence can contribute to an understanding of how violence might be prevented, and what types of strategies for violence prevention have been most effective and how they can be implemented. The paper proposes a comprehensive model of school-violence prevention having three components: (1) creation of a safe and responsive school climate; (2) early identification and early intervention for students at risk for violence; and (3) effective responses to school disruptions or crises. The paper concludes with a discussion of zero-tolerance policies, stating there is little or no evidence that such strategies have improved student behavior or made schools safer. Instead, the paper offers a new model of school discipline based on early intervention. (Contains 20 references and 3 tables.) (WFA)