Wow, that's a hard one. The administration of course has every right to close down if they feel students and staff are at risk.
Should it be he call of the Administration of the school? I think it would have to be.
As a father of kids that age, I'd have to err on the side of safety, of course unless they let the kids
carry on campus.
Or have the faculty , custodians, etc, pack heat while they're at work.
I'd have to come down on the side of keeping the students and faculty safe. Set up roving guards and K9 units, maybe some trip flares, claymores, etc.