Three years ago, the University of Nebraska’s Board of Regents, eager to find more funds for undergraduate need-based financial aid for students at its flagship campus in Lincoln, struck a deal in which the National Education Loan Network, would provide loan funds that the university would administer to its graduate and professional students. As part of the arrangement, authorized through a process known as “school as lender,” Nelnet, as the Lincoln-based lender is known, would give the institution more than 6 percent of the profits to use for need-based aid...