Following the deadly shooting at Marjory Stoneman Douglas High School, administrators reached out to former Columbine High principal Frank DeAngelis for guidance.
There's no book to teach what DeAngelis learned after gunmen killed 12 of his students and a teacher in 1999.
He told Stoneman Douglas administrators there should be no balloons at their welcome back ceremony Wednesday, because some popped at Columbine's, sending students diving for cover.
He said substitutes should be onsite in case teachers need time to recompose themselves.
He also advises changing the sound of the fire alarm, which got pulled at both Columbine and Stoneman Douglas during the shootings. Otherwise, it will cause panic.
DeAngelis says everyone must understand that they must redefine what's normal, because survivors will never return to what they were before the shooting.