*late*
Like after there was a school shooting here (the first big one in the country, pre-Columbine), security in the schools was upped like crazy here. It did nothing more than make the parents feel safer, and the students feel annoyed. Lightning doesn't strike the same place twice. We had photo IDs, colour coded for grade and wing of the school you were meant to be in that had to be worn around our necks at all times. We had to carry clear backpacks. All visitors had to check in upon entering at the main entrance and get a visitor badge. All other doors were kept locked the entire day. No one was allowed outside unsupervised. If you tried to wander around the school during lunch (to go to the library or the bathroom or anything), you had a security guard interrogating you about where you were going. It was overkill, and after a few years, they let up on most of it.
But the thing is... these efforts, had they been in place prior to the shooting, would not have prevented it. It happened in the morning before school had even started, when students were freely loitering in the lobby, and wouldn't have even been wearing their badges yet (they were picked up and put on in homeroom). The clear backpacks we had to use were clever but not totally safe. Anyone could've still hidden weapons inside, between books where they wouldn't be visible. The shooter here had carried his in wrapped in a blanket, telling people it was a science project. Afterward, in such a situation, a security guard might've looked under the blanket. Might've.