I don't know. I went through air raid drills at school when I was a kid. At the time, the Soviet nuclear threat was very real. Of course, some drill tactics, like hiding under the desk, would not have prevented carnage in the event of a nuclear strike, but at least we were being prepared. And I don't remember being traumatized in any way by the drills.
Parents are raising their kids to be snowflakes. These are dangerous times. I think the kids have to be prepared for everything. Does them no good to be shielded from bad things like school shootings. And perhaps these drills could save their lives.
And yes, there has to be armed security at the schools too. No more of this "gun-free zone" crapola.