I’M ALL FOR PREPAREDNESS, but this sounds like very poor judgment on the part of the teachers:

Staff members of an elementary school staged a fictitious gun attack on students during a class trip, telling them it was not a drill as the children cried and hid under tables.

Of course, if the kids, or some adult who happened to come across this, had responded violently, that would be the teachers’ fault too. (Via Volokh). It was meant to be a “learning experience,” and if nothing else, I think the students learned a valuable lesson about the adults in whose care they had been placed.

UPDATE: More thoughts here.