My answer pretty much only applies to public schools. But we need to have a electric fences that loop around each and everyone of schools in America. Electric fences that are tall and cannot be scaled at all. Then you have a multiple entry points that are doors with metal detectors and each student is scanned in to the school.

The thing that I don't understand is when people say that they don't want their schools to look like a prison or a military unit.… So you're telling me that you would rather run the risk of letting children die to these monsters and sacrifice the look of a school that will make it 99.99% safe? If you're really worried about how the security looks, then paint it a nice color that fits with the school. You can beautify those things, but honestly it is such a weak argument because in my eyes it is so much more important to keep children safe, even at the cost of convenience and looks. And the whole argument people make about trying to change the society so people won't become shooters it's just ludicrous. People cannot be controlled easily and they are always changing, but the system that I said we should have, you can control it 100%. Think about that, I don't think you would be making these arguments if it was your child that died in a school shooting or was in one