I've known two. Decent, super smart really good families. None better.
I also know a liberal who rented out her townhouse in D.C. to the graduate student children of what she called good black families. $30,000 worth of damage later she found out that even though the parents were doctors, lawyers, business owners, etc. who summered in Oak Bluffs, their kids were trash.
It’s called “reversion to the mean”. It’s what happened to so-called “bourgeois black” Prince George’s County. I have read of a study which compared data from Prince George’s County to a county in West Virginia. The white males in the West Virginia county came from families with lower socio-economic status than the black males in the study from Prince George’s Co. But the black males from two-parent, higher earning families in Prince Georg’e Co had lower school scores, higher drop-out rates, and higher crime rates than the white males from poorer families in the West Virginia Co. I have tried to find this study in my bookmarks, I seem to recall having read of it on the “La Griffe du Lion” website.