We have forgotten that as parents we are the primary custodians of our children, that the chief job we as parents are to train our children
This is just about the only truly accurate statement in your post. Quite simply, the body of students in highly performing schools do well because their parents expect them to do well and help them to do well. The parents take time to help their kids learn, and they do not make excuses for poor results.
Unfortunately there's no way to compel the parent to do the right thing. If we want that right thing done, we pay for before-school and after-school programs, and we attempt to steer the kids in the right direction. Unfortunately that is difficult because schools are hampered in the discipline that they're allowed to use, and teachers get disillusioned working in underperforming schools.
I think the solution is to reduce class sizes and to essentially tie teacher pay to a combination of number of free-and-reduced kids in their classes and at the school and performance relative to the pupils' previous years. Basically if you're at a school in a very wealthy neighborhood, you aren't going to make as much money as those schools are no challenge by comparison, but if you're in a school with lots of Title 1 kids, you make more. This encourages veteran teachers to take on the harder schools, but ties incentive pay to the improvements they can make.