Less than a month before the start of the semester, Ph.D. students at Columbia University in New York were told with little explanation that they would no longer be teaching this fall.

The catalyst for this change is unclear. The university said it’s an effort to reduce the teaching load on Columbia graduate students and allow them to finish their degrees in six years rather than seven. The students said it’s a move to weaken the labor power of their union, which is in the middle of tense negotiations with the university to renew its contract, which expired June 30.

The students, who are members of the graduate student union Student Workers of Columbia, will still be paid. However, instead of receiving a biweekly teaching stipend, they’ll get a lump sum at the start of the semester. To pay both the Ph.D.s and their replacements, “the cost to the university likely runs to millions of dollars,” estimated Michael Thaddeus, a mathematics professor at Columbia and vice president and acting president of the Columbia chapter of the American Association of University Professors. In July, Columbia agreed to a $221 million settlement with the federal government in order to restore hundreds of millions in federal research funding.

Columbia has traditionally tapped sixth- and seventh-year graduate students to teach foundational courses and some of the undergraduate college’s Core Curriculum classes, which includes courses, like University Writing and Frontiers of Science, that all first-year students are required to take. The work is more time-consuming than a regular TA job; as the so-called instructors of record, the Ph.D. students must teach two two-hour lectures and attend a pedagogy seminar each week, on top of all of the reading and prep time that goes on behind the scenes. The workload sidelines their research and writing, a representative from SWC explained. But it offers valuable teaching experience, and Ph.D. candidates are usually guaranteed a seventh year of funding when they sign on to teach a core class.

But this teaching expectation is unusually large for graduate students, according to Columbia officials.

“Columbia doctoral students have typically been required to teach more than Ph.D. students at peer institutions, which often means delays in their time to degree,” a university spokesperson wrote in a statement to Inside Higher Ed. “After discussions with some departments about teaching requirements and instructional staffing, we have released some graduate students from teaching obligations for the fall—while continuing to offer them the same funding and benefits. These students will have more time to complete academic requirements or advance their dissertation research and writing.”

Neither the students nor some faculty buy this explanation. Students say they didn’t receive any formal communication about changes to the graduate student teaching structure and that the move to dismiss or deny Ph.D.s from the teaching positions is an effort to undermine the labor power of the union, which had been planning a strike for the fall. As TAs and members of SWC, the students would still be able to participate in a work action, but it wouldn’t have as big an impact as lecturers walking out of class.

More than 100 students are affected by this change, according to the union. Columbia officials said the figure was much lower but declined to share an exact figure and noted that the number of Ph.D. core instructors varies year to year.

Columbia’s AAUP chapter denounced the university’s action in an Aug. 19 statement.

“We do not agree with the claim that this step has been taken to help graduate students. Rather, it clearly has to do with the looming contract negotiations. The timing makes this clear,” said Thaddeus. “Students applied for preceptor positions back in November, and then they heard nothing at all for many months. If this were being done to help graduate students, then it would have made sense to notify them promptly.”

The move will also damage the quality of Columbia’s doctoral and M.F.A. programs, Thaddeus argued.

“Practical experience with setting assignments and exams, giving final grades, and so on is invaluable to those graduate students who pursue a career in teaching,” he added.

One sixth-year Ph.D., who wished to remain anonymous to prevent retaliation from the university for speaking out, applied for a core teaching position in December. Over the next eight months, she received no communication about the position and finally received an offer for a TA position July 30. It wasn’t until Aug. 6, the day she was originally supposed to sign and return the teaching assistant appointment letter, that she heard back about the core position. She’d been rejected, the email said, and it included no explanation or information about the widespread changes to graduate teaching duties at Columbia.

The abrupt change is “really disrupting people in the later stage of the program, like myself, who thought that this was not going to be my last year,” says the Ph.D. student. “Now I’m having to go on the academic job market basically at the last minute.”

To fill the now-vacant teaching jobs, Columbia is recruiting for one-year lectureships and advertising the roles to adjuncts, postdocs and New York–based graduate students at other universities.

“I wanted to share with you a posting we’ve just made for full-time lecturer positions teaching all across our Core curriculum—in Art, Music, Literature, and Contemporary Civilization—where we are expecting a larger entering class that we’d originally thought,” Columbia officials wrote in a message that was passed along to faculty at the University of Chicago and obtained by Inside Higher Ed. Columbia has also sent the position to Yale University.