Are there any good statistics on students who are second generation in higher education?
What you need is studies that control for parental education. If none of them have a university education then they are the first generation, if one of them has a university generation then they are not the first generation. So the "effect" of that variable makes the comparison you are after. Parental education is a fairly standard variable in this literature, so you should be able to find such references quickly enough.