Originally Posted by HowlerKarma
That means that there are households in the middle two quartiles who are there by CHOICE, not by circumstance, and for most purposes, we don't really belong there, but in the upper quartile instead.

That's an interesting point.

Regarding the language development topic and the relevance to achievement, I am wary of the fundamental importance. In light of the adoption studies that have been performed, we know to expect the importance of environment to be exaggerated in childhood.

Also, I read through the page that ultramarina linked, and I noticed discussion about low SES families that were highly talkative, and high SES ones that weren't. It made me wonder: did they give the parents IQ tests?