School bullying, also referred to as peer victimization, has increased rapidly in recent years and can be extremely harmful if schools and teachers do not establish effective bullying-prevention programs. Recent data on the number of students who are victims of bullying indicate that between 30 and 80 percent of students in schools report being targets of peer victimization. The concern that educators have about bullying has led to many studies that have refuted common beliefs about peer victimization. This article discusses what bullying is, why bullies mistreat others, and how schools and teachers can respond effectively to the problem.