But the march wasn’t celebrating the long history of Jewish labor activism. Instead, the crowd was protesting labor practices at JTS, Conservative Judaism’s flagship academic institution.

The protest’s target is a 100,000-square-foot construction project dubbed the “21st Century Campus,” which is replacing the JTS library with a new library space, a performing arts center, classrooms and a residence hall. JTS is billing the new space, slated to be finished in 2019, as a step into the future.

But protesters say the contractor managing the project, Gilbane Building Company, doesn’t treat its workers well, hiring subcontractors who skimp on wages and violate safety standards. They also complain that because Gilbane does not work exclusively with union subcontractors, the seminary is violating a legal ruling by the Conservative movement mandating that Jewish institutions strive to employ union workers.

“Choosing a contractor that would openly, in any way, harm the lives of workers is really troubling,” said Lili Brown, 20, a junior at List College, the seminary’s undergraduate program, who participated in the protest Monday. JTS, she said, needs “to recognize that the labor that goes into this project, that people benefit from, is a really important thing to consider.”

JTS Executive Vice Chancellor Marc Gary rejects the protesters’ claims and says that Gilbane’s labor policies exceed industry standards. Gary notes that the Providence, Rhode Island, firm has won several awards in recent years for its safety record and overall performance. He adds that Gilbane’s emphasis on green building as well as equal-opportunity employment made it attractive.

“We chose them for their safety record, which is superb,” Gary, also the chief operating officer, told JTA on Monday. “We chose them because they have a lot of expertise in educational institutions. They have an excellent reputation among other contractors, other developers.”

The protesters, who were organized by an advocacy group called the NYC Community Alliance for Worker Justice, have clashed repeatedly with JTS over the past few months. The group first protested in front of the seminary in February, and followed up with protests in early April and again on Monday. Gary has held several meetings with students, faculty and community activists to discuss the dispute.

On Monday, protesters attempted to deliver a letter to Gary outlining their concerns. Eddie Jorge, a coordinator for the advocacy group, said they plan to place a large inflatable rat — a symbol of union protests — outside the school this week.

“What’s important to them is not whether the workers on the job have any standard of dignity,” said Liana Kallman, an organizer with the Community Alliance. “It’s not in the budget.”

Gilbane’s safety and wage record is at the heart of the disagreement. Gary points out that the company won construction safety awards from industry groups in 2013 and 2015, as well as an Excellence in Construction award from the Association of Builders and Contractors in 2015. And he says Gilbane has committed to paying its workers a living wage — a minimum of $15 to $20 an hour in New York City, according to an MIT study.

Gilbane would not comment for this article, referring JTA to Gary.

But activists from the NYC Community Alliance say Gilbane’s record in this city falls short of its performance nationally. They point to a string of safety citations at Gilbane job sites in New York this year — including a fence collapsing twice at the JTS site.

Robert Schwanemann, a construction worker who worked on a Gilbane site over a period of 10 months, said the site had insufficient harnesses, and some of his colleagues lacked training. The training and safety issues would have disappeared, he said, had Gilbane stuck with union subcontractors.

“It’s about humanity,” said Schwanemann, who worked on a Gilbane site from 2015 to 2016. “They’ve got these guys they’re hiring with no sort of expertise, and they haven’t been through any real apprenticeship program in terms of learning how to do your job with skill, quality and safety.”

Gary says Gilbane’s “open-shop model” — wherein it accepts bids from both union and non-union subcontractors — allows companies to be chosen based on merit. But protesters say that decision runs against a 2008 ruling by the Conservative movement’s Committee on Jewish Law and Standards, which urges Jewish institutions to fulfill the imperative to treat workers fairly by hiring union labor and paying a living wage.

“Unions appear to be the most efficient means of guaranteeing that workers can live on their salaries, care for their health, and avoid taking second and third jobs,” says the ruling, written by Rabbi Jill Jacobs, who was ordained by JTS and now heads T’ruah: The Rabbinic Call for Human Rights. “Jewish employers should allow workers to unionize, in order to help all workers in the industry attain higher wages and benefits.”

When that ruling was passed, Gary wrote a partial dissent, saying that hiring only unions allows Jewish institutions to discriminate against employees who choose not to organize.

“If we truly respect workers, we should respect their choice to join a union or to refuse to join a union,” he wrote. “We should not inhibit a worker’s job opportunities because he or she made … the ‘wrong choice.’”

To ensure that the construction work will meet acceptable safety standards, JTS will hire a safety coordinator from the city government. It will also draw up a safety plan, which Gary said will be published in advance of construction work resuming this summer. Gary has also met with Jacobs to discuss the project, and thus far she has refrained from commenting on the issue.

Students have had no such qualms. A letter written by alumni of the JTS undergraduate program circulated online Monday, quoting the Bible and admonishing the seminary for failing its own standards.

“Several sources in our tradition adjure us to protect the rights of those who are most vulnerable to exploitation, and deter us from benefiting from exploitative practices,” the letter reads. “Oppression can take many forms, including unfair compensation and unreasonable risk. Our tradition cautions us against both of these potentialities.”