[Clubber]

I would say Child B would be a lot more successful if he had drive than if he didn't. Same with Child A. I've known a lot of rich kids that didn't amount to squat. (I went to one of those elite private schools, but my dad was a teacher there, so we got steep discounts).

[Hermitian909]

Sure, but we're not comparing the child to themselves with and without motivation holding all other factors constant. The question is, if two otherwise equivalent children are placed in living situations of vastly different quality how likely are differences in drive going to influence success?

The fact that some poor kids succeed and some rich kids fail isn't nearly as important as the what percentage of these groups succeed and fail.