I obviously can't speak for everyone, but even when I was in school, I knew (thought) schools primary purpose was to babysit kids and teens so any damage they were doing was in a contained environment. Education was just busy work and safety is definitely a goal but a difficult objective.

When I went to college, I met friends with dramatically different experiences in their schools than I had, and that was the first time the idea that school was more than just a babysitting camp had crossed my mind. My school was safe from exterior threats, and they took the bomb threats and jail breaks very seriously, even holding us in our classrooms late into the day until the perpetrator was caught, but internal threats caused by kids would always outnumber the teachers capacity to thwart. My parents choose where we lived based on the school having the least violence in the area so I know my experience wasn't even on the extreme end.

Edit: I realize I didn't address education. In short, in successful because my mom put a lot of work trying to educate me and ensure I took homework seriously. Even though I hardly attended my classes, I graduated top 10% because submitting homework was all you needed to do to surpass your peers. Any kids whose only educational influence was school itself, at least where I grew up, didn't receive much of an education.