There are parents at all social levels who are very involved in their children's academics and view the school system as only one component of their children's academic achievement (and as a consequence their chances at succeeding professionally).
There are other parents who see the school system as _the_ only tool and the only institution with the responsibility to educate their children --that is a great mistake and to the detriment of their children. I've seem this parental attitude in both poor parents and middle class parents.
I've been places where every extra penny earned by a parent go to their children --they forgo any non essentials in their lives in order that their children have a better chance. They more or less see the escape from poverty as a multi-generational effort and are willing to put their part in wholeheartedly. In exchange, the parents have expectations from their children as the parents enter old age.
So, academic achievement can be reached even for the poor kids, so long as their society and the individuals accept other means of achieving this end.
It happens with some immigrant groups within the US as well, so it's not unheard of in the US. And it's not only the economically privileged who can achieve academically.