That's the logical fallacy of what you propose though. That anything short of a TSA style system at schools would be able to delay or stop a determined crazy person with any sort of consistency or regularity. I'm ok with optional security / police that some campuses opt for.
Unless there is a massive security force monitoring schools though, the likelihood of something like this being prevented is minimal and not worth the state / federal spending. If local cities / counties want to run with it and raise taxes for a campus security measure that should be up to them.
A discussion about how to keep guns out of crazy people's hands would be more beneficial than discussing security systems of limited usefulness.
I would argue that the TSA system is extremely bloated and overall unnecessary simply based on the evidence. Off hand I can't think of a single thing that the TSA has prevented from happening and I seriously doubt that they keep such things under wraps. Thinking of the shoe bomber, underwear bomber, etc. I don't recall the TSA playing any part in preventing those guys.
I suppose we could look at Virginia Tech, they probably have some sort of campus police force or security but also I feel that it's hard to compare as VT is a large campus, surely it would be easier to police a relatively small school.
You have made your opinion pretty clear but I think that you should consider a few more things. For example I was thinking of the homicide rate in the US, which isn't too extreme, Wikipedia said it was like 4.5 or something close to that, then I was thinking of how many police officers we have already and what the ratio was of homicides to officers. Of course school shootings are rare and thus the homicide rate for them would be much lower, I didn't come up with an actual number but it was clearly lower than the overall number. Then I also looked at how many police officers that we have, which was a bit tough to find as I see a lot of numbers listed as "law enforcement personnel" and such so it's hard to say.
It was clear that an extra 135,000 police officers would be a dramatic increase in the police force but with a budget of $8.1 billion it didn't seem like much to me honestly. In reality there would be a lot of overages and corruption I'm sure, I doubt my $8.1 billion would hold up for very long. Maybe I'm missing something huge but it basically seems like the cost of hiring one additional teacher per school, that's not much.
Basically it boiled down, at least in my mind, of what a school should provide to us and our children. Of course the first and most obvious thing was an education, but after that was security. A school should be a place where a child feels secure and safe, doesn't have to worry, and can learn their little heart out. And the same applies for parents, and hell even grandparents and other family members. People should not be worried that their child is unsafe at school due to a clear lack of security.
As I pointed out in my argument: Are minor traffic and parking violations really more important than security and what should be the second safest place for a child? I don't think so.