Senselessness and Safety

Regardless of where you stand on 'gun rights', (and to be clear, I own a few) any time there is a senseless shooting it seems reasonable to ask, how can we prevent this happening again - (and again and again)?

But I'm confused. Don't we pay taxes that are supposed to support our school systems? So here are my questions.

I know that schools are frequently saying that they don't have enough money for supplies, books, whatever. How is it that we can send so much money overseas or be concerned about illegal immigrant children, but not FIRST take care of the needs of our own american citizen children?

Why don't we have the same sort of security at schools that we do at other 'Government' buildings? Why can't we simply lock the doors? Now wait, I know fire - but what I mean is - why can't we lock the doors so they cannot be opened from the outside - but will open from the inside?

Arrival time of students would need to be during a 'window' of time. There could be ID cards. There are ways to do this. I've seen it. Why don't we utilize the same sort of systems for entry as is used in many office or apartment buildings? A person must be 'buzzed in', sign in or have an ID to get past the entrance. How hard is that?

Whether or not we want to focus on mental health, gun laws or whatever else - wouldn't it be a fairly simple matter to spend some of our own money, our own tax dollars to make our government buildings (schools) as secure as say a courthouse? I'd be 'for' spending some of the money I pay in taxes every year - for that.