When Wall Street heads to the classroom, the results aren’t great. That’s the takeaway from a working paper distributed this week by the National Bureau of Economic Research. The study, conducted by researchers at New York University’s Stern School of Business and the University of California-Merced, took a look at what happens when private equity firms buy up for-profit colleges. The results: students are worse off and the college’s reliance on federal student loans and grants goes up.