There's actually a book that talks about this - http://www.amazon.com/gp/product/04...89&creative=9325&creativeASIN=046501867X

And another - http://www.amazon.com/Nurture-Assum..._1?s=books&ie=UTF8&qid=1302557891&sr=1-1

Studies -
http://www.newscientist.com/article/dn1520-iq-is-inherited-suggests-twin-study.html
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7610.2011.02421.x/pdf


Of course, none of these suggest that a terrible home environment won't cause poor school performance. However, what we are seeing in the divide mentioned in the original article is more than can be explained by children in extreme environments, IMO. Most families in lower socio-economic situations have more stress, and probably more time out of the home, but most are not in abusive/destitute/horrific situations. Those situations are rather rare in the US. Here, a "poor" family will, more than likely, live in a single family apartment or home, own 1-2 cars, have more than one television, internet access, cable tv, cell phones, etc, etc, etc.

~amy