A new study in the American Sociological Review shows that the more money parents pay (both in total, and as a share of total costs) for their kids to go to college, the worse those kids do in their classes. The author, Laura Hamilton, points out that parental investments "create a disincentive for student achievement." Hamilton's results weren't entirely one-sided: she found that while the wealthier kids had lower GPAs, they had a higher graduation rate.
This seems like a classic case of incentives and training: wealthy kids didn't have to work as hard to be where they are, and can feel reasonably assured that as long as they can muddle through their classes, they will be okay once they are out in the real world where hard work helps, but so does money. Kids that may be working to pay for school know the (monetary) value of the education they are getting, so they work to get the most of it.
While this is a fun rich-kids-get-their-comeuppance finding, it speaks more to the structural incentives of the education system and the economy as a whole. Hamilton's study is a valuable statement in a much larger conversation.