I've also read some very interesting ethnographic studies about the effects of poverty, including ones about the parenting styles of different class levels.
The most staggering (to me) finding was that poor African Americans (not just blacks — specifically Americans) ask their small children fewer questions that the parents already know the answer to (e.g. "What's that?? Right! That's a kitty!"), say "No" way more often, and expect unquestioning obedience rather than questions, exploration and creativity.
Lower class whites also trend that way in their parenting styles, but not to the same degree.
And of course, parenting styles tend to transfer from generation to generation. Thus the whole "I'm becoming my mother" and "I want to be a better father than my father was" cliché, heritability of depression and also the legacy of child abuse.
When you think that yeah, really, in terms of the number of generations, it was not long ago at all that these people's ancestors were bought and sold like property.
Combine the slavery aspect with the parenting aspect -- and the fact that parents act like their parents -- and you can see how, as a race in America, those kids could be behind, even if their families are much wealthier now.
Their parents' parents probably were not. To say nothing of their parents' parents' parents.
It was this realization I had, more than anything else (in addition to a visit to London), that made me realize that American society truly was racially biased -- at a much deeper level than most people talk about.
These sociological findings are not new or obscure -- and yet, there are so very few programs to help break the cycle by helping those families improve their parenting.