Years ago after one of the horrific school shootings. The NRA and other organizations recommended having schools hire retired law enforcement "Part Time", each doing just a couple of days a week (so it would not affect their pension). Many thought this was a fantastic idea a retired L.E.O. doing say 2 days a week tops, to help protect kids and put a little spending money in their pockets. Another positive thing with this, is benefits would not be necessary. Retirees keep their medical insurance upon retirement and wouldn't need other benefits because it would be part time up to 16 hours a week. The big reason this got shot down is, the majority of schools are public and run by anti police & anti military socialists. I personally think it's a fantastic idea; one that the public should push for.
I get what you're saying, I really do.
But if the thought is countering an active threat, I'm not so sure even I am the best to do it at this point. I don't shoot as often as I'd like and dynamic defense requires training. I'm not as quick on my feet due to substantial injuries to my back and lower body.
My take on it is that you are more likely to individually win the Powerball than be involved in what I would consider a 'school shooting', even if you consider the last couple of years. They simply do not happen as often as the 'news' would like you to believe.
What I consider a 'school shooting':
The school/children in general must be the target, not a specific person with collaterals.
It can't be a 'domestic', romantic partner is the actual target, even with collaterals.
It can't be targeted to a particular person or group, ie gang related.
It has to be during normal school hours, on the actual campus. This eliminates football games/sports for the most part.
It has to be a general attack, no individual targets, then I consider it a 'school shooting'.
There is some wiggle room in my broad definition, but you get the point.