The school counselor was a subject matter expert in counseling students, not divining the parents armed the little terrorist, not invoking x-ray vision to figure out kid brought the negligently unsecured weapon to school. You want to know who the experts were for that kid? The ones who raised him, who spent every day with the kid. They should have known what was going on, they should have warned the school he had access to a gun.

You keep saying the school should have culpability. For what? Not forcing the parents to take a kid they refused to bring home? For not taking the kid to another classroom, where he would have just started shooting anyways? No, the parents refused to take responsibility for their child and the school had /no/ means of forcing the minor off campus if there was no legal guardian to take custody.

School officials aren't omniscient. Nor are they free to violate the civil rights of kids whom they have no just reason to illegally search or detain. The parents did, could have, but didn't.