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. So far this year, there have been at least 24 acts of gun violence on K-12 campuses during the school day.

The count now stands at more than 311,000 children at 331 schools.

311,000 kids are going to grow up with strong opinions about guns. Hopefully they'll end this madness.