More than 311,000 students have experienced gun violence at school since Columbine

The Washington Post has spent years tracking how many children have been exposed to gun violence during school hours since the Columbine High massacre in 1999. Beyond the dead and wounded, children who witness the violence or cower behind locked doors to hide from it can be profoundly traumatized.The federal government does not track school shootings, so The Post pieced together its numbers from news articles, open-source databases, law enforcement reports and calls to schools and police departments.While school shootings remain rare, there were more in 2021 — 42 — than in any year since at least 1999. Using Nexis, news articles, open-source databases, law enforcement reports, information from school websites and calls to schools and police departments, The Post reviewed more than 1,000 alleged incidents but counted only those that happened on campuses immediately before, during or just after classes.Shootings at after-hours events, accidental discharges that caused no injuries to anyone other than the person handling the gun, and suicides that occurred privately or posed no threat to other children were excluded.