I don't think anyone will be shocked to learn that kids with rich parents are more likely to graduate from college than kids with poor parents. But the fact that the gap is increasing—and increasing quite rapidly—is pretty striking.
I got this chart from a new report (PDF) by Lane Kenworthy and Timothy Smeeding:
This is a real case of inequality as such. Low-income kids are more likely to both attend and complete college than they used to be. But the increase in the completion rate has been relatively tiny, while for high-income families it's been enormous.