The bystander is defined as an active and involved participant in the social architecture of school violence, rather than a passive witness. Bullying is redefined from a triadic (bully-victim-bystander) rather than dyadic (bully-victim) perspective. Teachers, including administrators, and students can promote or ameliorate bullying and other forms of violence when in this social role. Cases are used to illustrate this phenomenon, including one in which a teacher is murdered. Data are presented from a study of teachers' perceptions of other teachers who bully students, suggesting that bullying of students by teachers and bullying of teachers by students is a factor in the aggravation of school bullying and violence that needs to be more openly discussed. An intervention in nine elementary schools involving 3,600 students is outlined to illustrate how a focus on reflective mentalizing and awareness of the importance of the helpful bystander role can promote a peaceful school-learning environment for students and teachers. The paper concludes with an outline for research into how communities and schools adopt bystanding roles when faced with complex problems like youth violence, and how they may avoid facing the problems by blaming law enforcement and educators.