Is there causation between no high school diploma and lower wages? They are certainly correlated.
And unfortunately for them, it doesn't keep them from inflicting the same life-outlook on their offspring. Greatest tragedy of our society, that we overlook that.
I'll leave it to the smart statists out there to figure out how to remedy this tragedy whilst staying within the "moral framework" they have in-place already. You know, the thing that makes it "illegal" to carry bad-plants in your pocket while simultaneously making it legal to bring innocent life into this world without being able to take care of it, and ultimately making it suffer.
Yes, there are rare people who have never finished high school and had material success, probably most drug dealers who cashed out and bought franchises or real estate. So logically then general causation is ruled out.
But for most people without high school degrees it's extremely difficult to disassociate their lack of education with later material success.
In the year 2015, graduation from high school is a much easier in almost all ways. If you can't manage to graduate there is something seriously wrong and I probably don't want to hire you.
This is why I'm always terrified of trying to push more and more people through educational hoops: the ones who don't make it are that much more weird and excluded.