The University of California at Santa Cruz fired 54 teaching assistants Friday who refused to turn in fall semester grades in an ongoing strike for higher wages.

“It is extremely disappointing to us that we have to take such a drastic step, but we ultimately cannot retain graduate students as teaching assistants who will not fulfill their responsibilities,” Lori G. Kletzer, the school’s executive vice chancellor, wrote in an email to the campus Friday.

Graduate workers launched a grade strike, withholding final marks for undergraduate students, in December in a bid to force administrators to negotiate a cost-of-living wage adjustment. When that didn’t work, teaching assistants went on a full strike this month with daily protests that led to arrests.

University administrators gave graduate workers until Feb. 21 to submit grades or lose their teaching appointments for spring semester. According to the university, 96 percent of grades were submitted.

University spokesman Scott Hernandez-Jason said the 54 students will not face expulsion and can continue their coursework. Still, their tuition and fees will no longer be covered as a part of their appointment. Strike organizers say it may be impossible for many to remain in school.

“The financial implication is totally devastating,” said Melissa Cronin, an organizer and doctoral candidate in the Department of Ecology and Evolutionary Biology. “For a lot of those people, this is their only source of income. The combination of loss of income and staggering tuition is disastrous."

Cronin estimates that one-fifth of the teaching assistants who received notices are international students who could lose their visas. She said people were willing to risk their education because of how dire living conditions have become as graduate students are priced out of the housing market.

“People are living in their cars. They don’t make enough money to buy food,” Cronin said. “For so many people, this was the culmination of months or years of continuing to slide into poverty. And something just broke.”

Graduate workers at UC-Santa Cruz say a raise of $1,412 a month would make it easier to afford housing in one of the most expensive rental markets in the country. But university administrators say their hands are tied because of a contract with the United Automobile Workers, the union that represents graduate students at all 10 campuses of the system.

“While I’ve disagreed with the tactics the graduate students have used to communicate their concerns, I do not want to downplay the gravity of those concerns,” Kletzer wrote.

She noted that the university is creating two temporary housing programs and providing an annual $2,500 housing supplement until more campus housing becomes available for graduate students.

Strikers say the measures are insufficient and not a sustainable solution.

Faculty and undergraduate students have protested alongside graduate workers, whose plight has garnered the attention of Democratic presidential candidate Sen. Bernie Sanders (I-Vt.). He tweeted out support for the students this month and expressed disappointment Friday in the university’s decision to dismiss dozens of teaching assistants.

“This is disgraceful,” Sanders said of the dismissals. “All workers deserve the right to bargain and strike for better wages and benefits. To Janet Napolitano and @UCSC: stop this outrageous union-busting and negotiate in good faith.”

The students have been waging a wildcat strike, meaning there was no sanctioned vote to take action. Still, union leaders have asked the university to consider adding a provision in the existing contract to address the cost-of-living increase. The UC system rejected that proposal.

Tensions between UAW Local 2865 and the system erupted this week when university leaders filed a labor grievance against the union for not doing enough to stop the strike. The union countered with its own filing accusing the university of illegally negotiating with students.

“We’ve done quite a bit to communicate to workers that this is not an authorized action,” said Kavitha Iyengar, president of UAW Local 2865. “We’re trying to get the university to come to the bargaining table with the union because without doing that, we’re going to see more of these illegal actions."

Iyengar said graduate workers across the UC system are threatening walkouts in solidarity with the Santa Cruz teaching assistants. Graduate workers at the University of California at Santa Barbara went on strike Thursday, while those at the University of California at Davis have begun a grade strike demanding cost-of-living wage adjustments.

Strike organizers at UC-Santa Cruz say 524 graduate students have pledged not to accept positions vacated because of the dismissals. Many are considering withholding winter grades in protest.