The University of Wisconsin-Madison is one of the most affordable, but with only 15 percent of students receiving Pell Grants, more work needs to be done, reports NPR.

America’s top public universities, known as flagships, are generally the most well-resourced public universities in their respective states, but today, according to a report from the Institute for Higher Education Policy, only four public flagship universities are affordable for students from low-income families.

A huge part of staying affordable is prioritizing need-based aid at the state and institution levels, according to some of the most affordable schools in the study, such as the University of Wisconsin-Madison and the University of North Carolina at Chapel Hill, reported NPR.

UNC has the Carolina Covenant, a need-based program that uses grants, scholarships and a work-study jobs to cover college costs, including living expenses. The University of Wisconsin-Madison has a similar program called FASTrack.

Both universities say their financial aid programs have helped them recruit more diverse classes. “We not only would be a less diverse school if we weren’t focusing on need-based aid — we’d be a weaker school because the students who enroll here with need-based student aid earned the right to be here,” says Stephen Farmer, UNC’s vice provost for enrollment and undergraduate admissions.

Fewer than 15% of UW-Madison’s students receive Pell Grants — that’s about half the 30% rate at comparable four-year college campuses nationally. “We recognize that there’s much work for us to do to ensure that students … see UW-Madison as an institution that’s accessible and affordable,” says Derek Kindle, the school’s director of student financial aid.