That is how it was at my high school as well. But in all fairness if there were 3 on duty that day in our town then 2 of them had nothing else to do but hang out at the school.
I'd much rather have firearms around in places of need handled by trained professionals than not relying on the pay-for-permit public. That is not a back handed comment to those non-uniform public who take great pride and responsiblity in carrying so please don't take it that way. For every one of you there is several out there who have one to have one and have no business with it.