Eight graduate students were arrested Tuesday protesting the Republican tax plan outside the Capitol Hill office of House Speaker Paul Ryan (R-Wis.), the latest demonstration against legislation that students fear will make their education less affordable.

Graduate students say their taxes will skyrocket if a proposal to treat their tuition benefits as income makes it into the final version of the legislation. Universities waive tuition for graduate students willing to work as teaching and research assistants. Those waivers are exempt from taxation, but House Republicans want that to end.

“I can’t afford to complete my degree if the exemption goes away,” said Bill Russell, who is pursuing a master’s in cinema studies at the University of Southern California in Los Angeles. His tuition is nearly $37,000 a year, while his stipend is about $13,000. “There is no extra money to pay more taxes.”

Russell was one of two dozen graduate students, community organizers and adjunct professors who camped out in front of Ryan’s office Tuesday to speak out against the provision and other proposals they say would harm working families. Capitol Police spokeswoman Eva Malecki said officers arrested and charged nine people with crowding and obstructing. All were processed and released within hours of the incident.

Benjamin Groebe, a doctoral candidate in astrophysics at Washington University in St. Louis, was among those arrested. Groebe said he had to stand up for classmates who fear they would have to leave school if the tax exemption were repealed, even though he is at a point in his program at which he no longer pays tuition.

Tuition for the 2017-2018 academic year at the university’s graduate school is $50,650. Groebe and other research assistants receive a stipend of about $21,000 a year, money that is taxed by the federal government. If the tuition exemption is repealed, those research assistants would see their taxable income rise to more than $71,000, despite only taking home a fraction of that amount.

“I know a lot of people who just wouldn’t be able to afford that, and they’d have to drop out,” he said. “The Republican response to that would be, ‘Go take out more loans.’ Loading up on debt is not sustainable. I have colleagues with children, and it’s already difficult for them to get by on their stipend. Adding this tax is just not feasible.”

Nearly 55 percent of graduate students had adjusted gross incomes of $20,000 or less, and nearly 87 percent had incomes below $50,000 in the 2011-2012 academic year, according to the most recent data from the Department of Education. During that same period, 145,000 people pursuing master’s and doctoral degrees benefited from tuition waivers, the majority of which were awarded to students in science, technology, engineering and math fields.

In a letter to House and Senate leaders Tuesday, Peter McPherson, president of the Association of Public and Land-grant Universities, said the tuition exemption “is critical for developing the science and technology workforce pipeline that employers need to propel our nation’s economy forward.”

Tuesday’s demonstration, organized by the Service Employees International Union, arrives a week after thousands of graduate students staged walkouts in protest over the GOP tax plan. Aside from tuition waivers, students say they are concerned the House version of the tax overhaul would eliminate student loan interest deductions and curtail state and local tax deductions to the detriment of public higher education. They are also concerned that House Republicans want to consolidate higher education tax credits in a way that would largely cut them out of the benefit.

The Senate bill that passed Saturday would not touch the interest deduction or tuition waivers, and several Senate Republicans have said they doubt those provisions would make it into the final tax legislation. Still, graduate students say they must remain vigilant. Even if the GOP hands President Trump a bill that excludes many higher education provisions, the impact that tax reforms could have on working families is of great concern, Groebe said.

“There is a lot to be upset about in this bill,” he said. “It’s a bill that takes from a lot of people in order to give to people who already have a lot. That doesn’t make any sense,especially now when it’s increasingly difficult for people to improve their standard of living. This is the last thing we need.”