One of the stupidest ideas I’ve ever heard.
1. Teachers could have been hurt taking cover.
2. Teachers could have been hurt trying to escape, like diving out a closed window.
3. Teachers could have hurt the intruders by tackling them, throwing things like chairs, books or even amped up on adrenaline, a whole desk, a computer monitor etc.
4. Damage to school property,
5. The knowledge that IN THE FUTURE it won’t REALLY be an intruder it will just be another test.