Hey,
you have written a very good post. But I disagree, that schools are the source of the problems of most of the failing teenagers.
I think schools are overwealmed by the multitude of problems some teenagers carry on their shoulders.
Usually their parents have a bunch of own problems keeping them from giving their children the support they would need.
Also most of the teenagers suffer from a lack of successes. Even if they did not have them in school before, it is alright if they had them elsewhere. But if they are used to fail they lose their wish to succeed. (I think you meant something similar when you wrote about previous problems in school)
After all, some students are though their parents and teachers give their outmost to care for them just so busy to master their puberty that academic success needs to weight for the second chance.
In Germany we call it the "second way of education" (zweiter Bildungsweg). Sadly most of the people who could benefit most, do not know that they have at every age the possibility to earn a higher degree.
My own parents did that - not to make career - rather to proove something to themselves.