Couldn’t you just start your killing spree after signing in? Once you’ve been buzzed in, what is signing a piece of paper going to prevent?
This security protocol is not for the crazed and criminally insane person. That is going to take armed personnel to deal with them.
What this security protocol is for - is related to the paperwork that you sign upon enrollment, which tells the school who is allowed access to your child. They are following that legal paperwork that was given at the beginning of the year.
It's a magic piece of paper.
You call the mother, the mother comes to the door, you let her in, she goes to check on her child, you throw a fit because she didn't "respect your authority" by coming before you and begging humbly your permission to see her child and call the cops.
These "procedures" do nothing to protect the children. They are all about the egos of the petty tyrants getting stroked.
That’s why they call the police if you don’t stop in at the office.