http://www.nytimes.com/2009/09/09/business/economy/09leonhardt.html?_r=1&ref=business
This article discusses the effect of college drop-outs in America. The author suggests that public universities should be added to the list of organisations whose failures have done most damage to the American economy in the recent years. He puts public universities in line with Wall Street firms and regulatory agencies that brought the financial crisis. It presumes that college drop-outs are a reason for the soaring of inequality and has slowed productivity growth.
This article is interesting in our discussion, since these findings are brought forward in the book ‘Crossing the Finish Line’, written by William Bowen (an economist and former Princeton president) and Michael McPershon (en economist and former Macalester College President). Again, economists seem to pop-up in a seemingly unrelated field.
Observing Economics 
Isn’t this more or less simply due to the fact that failing in private colleges is much harder?? From personal experiences, I have the impression that the high tuition fees of private collges almost guarantee graduation.