They push them, believe me. They might not actually graduate, but they still stick it out, and they are encouraged to stick it out. The result is that you've got a lot of kids who aren't going to graduate, and don't give a damn, and yet, there they are, they are gobbling up the resources and creating a learning environment that is bad for those who do want to learn.
Because they are given no choices, obviously. Yes, there are plenty of kids who would be far better off being apprenticed to a trade at age 14 or so, but we don't do that anymore.
Why ? Because of the PC bull that all kids are capable of going to college. So now college is dumbed down to accommodate these kids. Second reason why - the unions don't want the kids in the workforce, nor do they want unionized teachers done out of jobs teaching them.
It's not the fault of these kids that they are given no choices. The adults are the idiots for trying to fit square pegs in round holes.
The kids stick it out so they don't graduate ? Sorry, that doesn't make sense. All reports I've seen state schools push the kids out so they don't lower standardized test scores and drag the school into underperforming status.