There's an interesting phenomenon that happens in the US. Upward social mobility almost never happens, but in the rare instance when it does, those examples are given as proof of the "American Dream". The book Ain't No Makin' It (http://www.amazon.com/Aint-Makin-Aspirations-Attainment-Neig...) does a good job of explaining the sociological issues.
It's a fair assumption to say that bright kids from "tough backgrounds" are less likely to succeed. That's not on an individual level, but on a national level it's certainly true. For most, these are kids who saw their parents work hard and get nowhere. That's a special kind of demotivation that's difficult to shake by the time college rolls around. It's also why there's almost no upward social mobility in the US.
It's a fair assumption to say that bright kids from "tough backgrounds" are less likely to succeed. That's not on an individual level, but on a national level it's certainly true. For most, these are kids who saw their parents work hard and get nowhere. That's a special kind of demotivation that's difficult to shake by the time college rolls around. It's also why there's almost no upward social mobility in the US.