I'm a veteran urban school teacher, and here's my guess as to the general situation. Consider a class of 30 students. In that class:
5 students never attend school. They're on the rolls, but you'll never see them. Calls home aren't returned.
5 students attend two or three times a week. Naturally, they're all failing. Sometimes they'll just go to sleep when they're there. Sometimes they'll become disruptive.
5 students attend most days. But they talk continually in class. They use their cell phones whenever they feel like it. Those students are very disruptive, and often violent. The principal blames the teacher for not being more "creative", even though the teacher is following the mandated lesson plans exactly.
15 students are really great kids. Despite their poverty, they come to school with a good attitude. They want to learn something. But they don't learn much, because of the disruptive students.
I bet extrapolating that example over the whole universe would show there is little diviation to your observation. This is why I am a proponent of school choice. The parents of those 15 who obviously want their children to do well are being screwed by a system that just wishes to warehouse kids under the onus they need be educated till they are 16 or 18 depending on the state. When I was a child, 60 yrs ago, you acted up or got in legal trouble, off you went to reform school where you were perhaps taught a trade but you were removed from the general student population and ceased to be a disruption. Maybe that is the answer today but in reverse, let the good students go to a place where they can learn and leave the rabble in their inner city holding cells till they either reform and move on to prison.
So you’re saying eliminate half the kids so the other kids can get a decent education? I’m on board with that.