I'd like to know why you think that would be difficult.
lack of proper firearms controls
Very easily. I ve taught at a middle upper class public high school for years now and there is no, zero, zip metal detectors or any way for anyone to know if a student is packing
Not a crucial need~until someone is shot, that is.
Is this a recent shooting?
teachers and students stare at a cellphone.
These kids were serious about whatnot. If I had to guess on how someone could sneak a shotgun into school, I'd say he put it in an instrument case, or maybe got one that could fold basically in half when reloading.