Is your daughter often in trouble for messing around during serious situations?
Btw, it wasn't a "drill" as you insist on calling it. Those are planned, by the staff, and monitored by the designated officers. This was a full-blown evacuation.
Have you even stopped, once, while defending your precious flower's ears, to even imagine when the alarm went off, and the teachers knowing it wasn't a drill, heard it? In the wake of this week? That they, in loco parentis, possibly had very little time indeed, to save your children's lives?
But go ahead, carry on defending her. I do hope you come back and update us exactly on what her "messing around" really entailed.
As it seems extremely odd that the HT directed such wrath at your kid's yeargroup, you might be in for a bit of a shock.
But if you come back at all, I expect it will be to tell us the HT has been summarily horse-whipped and tied to the stake.
We won't believe you, like I don't believe your child's version of events now.