Associated PressAssociated PressAugust 21, 20165min274

When two students went on a deadly 1999 shooting rampage at Columbine High School, it not only shocked parents, students and teachers, it had a lasting impact on education. Copycat threats across the country have forced lockdowns and orders for teachers and students to shelter in place, and parents, teachers and students have spent a lot of time since learning how to respond to threats.