Fifty years ago it was more than rare to see in officer in our schools. And no the events today are different in that the students are certainly of another mindset toward authorities than fifty years ago...as well as their behavior when they are caught. Also students game the system to get each other in trouble.
Some schools have metal detectors but the vast majority do not. Most of your fears are overblown but typical.
Most people who do not live here think Chicago is completely crime-ridden. It isn’t. My neighborhood and its public elementary school are likely as safe as yours. I have no fear walking the streets at any hour.