As more states and localities in the U.S. begin adopting free college programs, a new study of England’s college financing system hints at some surprising pitfalls to getting rid of tuition fees.

The paper, which was distributed by the National Bureau of Economic Research this week, analyzes the effects of England’s dramatic shift over the past several decades from a higher education system that was free to students to one with relatively high fees that students typically finance through government loans. The study found that the country’s fee-based system created better-funded, more equitable universities and largely didn’t deter students from enrolling.

The reason behind the first finding — that fees allow universities to be better-funded — might seem obvious, but it can provide a cautionary tale of sorts to states and localities in the U.S. considering their own free systems. When the university system in England was totally funded by the government, lawmakers’ investment in the system failed to keep up with rising enrollment, said Gillian Wyness, a lecturer in economics of education at the University of College London’s Institute of Education and one of the authors of the report.

“One of the key challenges of a free system is how do you maintain funding to the sector,” she said. The introduction of fees in England changed that by allowing for another source of revenue, the research indicates.

It’s easy to see how this kind of outcome could be possible in a free college system in the U.S., given that as states and localities have faced budget pressure over the past several years, higher education has been low on the list of funding priorities for lawmakers. That’s created budget challenges for public universities that rely on government funding.

Wonder how we got to over $1 trillion in student debt? Watch this.

How higher fees created more equitable universities in England

The second finding — fees helped universities to be more equitable — seems counterintuitive. But introducing more money into the system through fees made more funding available for low-income students to help with their living expenses, Wyness said. In the earlier, free system, low-income students had access to means-tested grants and loans to help with living expenses and as the fees have increased so too has access to that type of funding help, the study notes.

What’s more, the funding constraints of a free-college system pushed lawmakers to cap the number of students enrolled at universities. A relatively recent decision to lift that cap created more opportunity for low-income students, the study found.

“When spaces are constrained it tends to be the wealthier students that get the spaces,” Wyness said. They’re more likely to have access to the resources that can prepare them to compete for those spaces, she added.

Raising prices comes with downsides

Though the fee system has largely worked as the government intended, it hasn’t been without pitfalls. A rise in fees about five years ago pushed many part-time students out of the system, according to Nick Hillman, the director of the Higher Education Policy Institute, a U.K. think tank. That’s largely because part-time students who tend to be older and have caring and other financial responsibilities, are more skittish about the idea of taking on debt than younger students coming straight from high school.

The decline in part-time students “matters to us because we’re leaving the European Union, so it will be harder for us to have skilled migrants,” Hillman said. That means there’s more pressure to train domestic talent, he said.

And, of course, the fee system is politically controversial, as the amount of outstanding debt in the country has skyrocketed. “There’s an ideological strand, particularly on the political left that education is a public good and therefore should be entirely free for everybody who attends higher education,” Hillman said. Over the past few months, the political conversation surrounding student debt and fees in the U.K. has gained new life after the leader of the left-leaning Labor Party promised to abolish tuition fees in a recent election and won more seats than expected. “Some people believe that was why they did so well,” Hillman said.

A key difference between British and American student loans

Still, Hillman and Wyness both agree that the study’s findings indicate a free college system may not achieve the desired goals of increased college access and equity in the U.S. that proponents are hoping for. But there are some key differences in the way American and British students finance college that make the fees less of a burden in the U.K., they note.

Across the pond, students use income-contingent loans provided by the government to pay for college. Borrowers are only required to pay back the debt once they’ve earned at least £21,000 (or about $27,000) and after that point, the loan repayment automatically takes a percentage of the borrower’s’ income, like a tax. Borrowers who never earn enough to repay their loans, see the debt wiped away after 30 years.

Though the U.S. offers income-driven repayment programs, borrowers don’t enroll in them automatically and many have reported struggling to access the plans. What’s more, any forgiveness under an income driven repayment program is taxed, so borrowers have the potential to be hit with a huge bill.

“Like so many areas of social policy, I would say England is somewhere between the States and Europe,” Hillman said. “We have loans like you do, but they’re more highly subsidized.”