Temple University is withholding tuition and health care benefits for more than 100 working graduate students who are on strike for better pay.

Some research and teaching assistants at the public school in Philadelphia received an email notice on Wednesday that their tuition remission had been revoked for the spring semester, "as a result of your participation in the [Temple University Graduate Students' Association union] strike." Tuition remission, a benefit offered by many schools to help finance employees' tuition costs, covers an average of $20,000 at Temple, according to the university.

Temple is now requiring the graduate students to pay their tuition balance by March 9 to stay enrolled in classes, or else accrue a $100 late fee.

"Employers threatening to cut off benefits is not uncommon, but actually doing it is," said Bethany Kosmicki, a member of the negotiating committee and a former president of TUGSA. "I was very, very disappointed to see that Temple is continuing these union-busting tactics rather than sitting down and negotiating for a contract with us."

Graduate students took to the picket lines on Jan. 31, after over a year of stalled negotiations between Temple and the graduate student union. The union is accusing the school of paying wages that fail to cover Philadelphia's cost of living. TUGSA has not responded to NPR's emails and direct messages.

Temple said in a statement on Thursday that students were warned that taking part in the strike and not showing up to work would cause them to lose their full compensation package, which includes tuition assistance and free health care insurance. Under Pennsylvania law, the workers who refuse to work are not entitled to compensation and work-related benefits, the university said.

Temple said that about 20% of union-affiliated graduate students have lost their benefits after going on strike, with the majority remaining on the job.

Kosmicki told NPR the number of students on strike is at least twice the number Temple is reporting.

In the past couple of days, she said, anger over the benefits cuts has spurred more people to join the picket line.

The union, which represents about 750 TAs and RAs, is proposing an annual base wage of $32,800, up from the current $19,500 average salary graduate students receive. Temple's proposal raises the base salary for graduate employees to $22,500 by 2026, according to TUGSA.

Union members are also calling for expanded parental leave, beyond the current five days allotted, as well as affordable family health care, which they say can cost up to 86% of their salaries.

"I've never known a year of grad school where I haven't had to take out some form of debt to be able to support myself nearby," said Kosmicki, a Ph.D. candidate in sociology. "I worry about things like being able to afford basic necessities, being able to afford my medical bills."

Temple said that students who return to work can get their benefits restored immediately.

"Returning to work does not mean individuals cannot picket or voice their concerns," university Communications Director Stephen Orbanek said in a statement to NPR. "It just means they must work to earn compensation and benefits, like anyone else."

Critics are calling the move a brazen tactic meant to dismantle union efforts.

"This retaliation tactic by Temple is unacceptable," Sen. Bob Casey, D-Pa., said in a tweet. "The right to organize—and to strike—is foundational in a democracy."

Philadelphia's city council on Thursday passed a resolution in support of TUGSA's demands.

The workers at Temple are the latest in a recent wave of labor protests by grad students who have gone on strike for better pay and working conditions, including at Harvard and University of California campuses.