I went to a pretty peaceful school in a low crime town but remember quite a few incidents of kids doing stupid things and boys being boys. Many of which likely broke some law or another. What’s the saying? The average American breaks 3 laws before they get out of bed? At any rate all of those incidences were easily handled with a visit to the principles office or a day or two of detention.
Remember one case in junior high we’re a kid got mad at me for some reason I can’t remember. He hit me, I hit him back and we exchanged a few additional blows. We were separated and got along fine the rest of the year. But I have read of some schools with zero tolerance policies were anyone breaking a rule that could be considered a crime gets carted off by the police. How would throwing me and the other kid in a cell with real criminals make anyone safer?
As for putting SROs in every school. The cost of that would be very high to staff every school in the nation. Most schools are only going to get one SRO. Anyone plotting an attack on a school would be able to easily determine their routine, when they are on break, etc. It would be easy for an attacker to avoid or take out that one SRO.
Plus the vast majority of schools will get by for years if not many decades or longer without needing a SRO on site. It seems far more effective from a cost and uncertainty factor to dissuade potential attackers to have unidentified staff on site and ready to respond if they are ever needed. Much of this could be accomplished with volunteers, donations and some minor equipment fees. With the proper vetting and training responding staff could be more effective than a single SRO or even a couple roving the halls with their sidearms on display.
Though for schools in high crime areas I could see the argument for having a SRO stationed in the school or on school grounds to deal with the daily gang related incidents.