NEW HAVEN, Conn. - Efforts to unionize graduate students at private universities are gaining momentum as the National Labor Relations Board shows new openness to arguments that they are not just students, but also school employees.

A union for teaching assistants is in place at only one private U.S. school, New York University, where the administration gave its blessing in 2013.

Since then, organizing campaigns have sprouted or gained new life at other major northeastern universities, including Yale, Harvard and Columbia. Students and schools around the country are closely watching the NLRB following its recent decision to reconsider its decade-old ruling that graduate student at private schools are not entitled to collective bargaining.

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At Yale, the Graduate Employee and Students Organization delivered a petition to the administration last month at the latest of several rallies since the NYU decision. Supporters in attendance included New Haven's mayor and Connecticut's attorney general and its two U.S. senators, all Democrats.

The Yale students are asking for recognition and for negotiations on issues including pay and benefits, mental health services and racial and gender equity among faculty and students.

"The argument that we're students and not employees falls flat for me when I think of how much time I spend teaching," said Michelle Morgan, a graduate student in American studies and a single mother who said she was hurt by a pay cut last year for upper-year teaching assistants. "My students see me very much as a teacher."

A Yale spokesman, Tom Conroy, said that the university provides some of the most generous support in the country, including full tuition fellowships, stipends and benefits, and that graduate students already have a voice in university affairs through student assemblies.

"Yale's longstanding position is that graduate students are students, not employees, and it would not be in the best interests of the students, the faculty, or the educational process to change the teacher-student relationship to a manager-employee relationship," he said.

Yale graduate students in their first five years of doctoral programs receive annual stipends of at least $29,000, nearly double the per capita income for the New Haven, which has a high poverty rate. But there is also a high cost of living, something United Auto Workers regional director Julie Kushner said helps to explain why the labor movement is percolating on campuses in the urban Northeast.

Public universities are governed by state labor laws, and the UAW alone has unionized tens of thousands of graduate students at schools including the University of California, the University of Massachusetts and the University of Connecticut. At private universities, covered by the National Labor Relations Act, the road to collective bargaining has been blocked by a 2004 ruling in a case involving Brown University in which the NLRB said students cannot unionize.

It was uncertainty over a possible reversal by the NLRB that led NYU to agree to recognize a union in 2013. NYU spokesman John Beckman said the university hoped the agreement would lead to a cooperative spirit but he said, without elaborating, that had not happened.

Last month, by a 3-1 vote, the NLRB agreed to revisit the Brown ruling, in a case involving a bid by the UAW at the New School in New York to unionize.

Most observers expect the board will overturn the Brown decision because it has grown more pro-union under the administration of President Barack Obama, said Daniel Johns, a Philadelphia attorney who specializes in higher education. He noted also that when the NLRB in August dismissed a petition by Northwestern University football players seeking to unionize, it wrote it was not establishing a precedent for graduate teaching assistants. For universities concerned about unionization, he said, now is the time to begin a campaign to persuade students it is not in their interest.

The organizing effort at Yale is affiliated with UNITE HERE, a union that already represents other workers at Yale. The UAW has been working with Columbia students and announced in September it had teamed up with students seeking a union at Harvard.

Allen Aloise, a dean at Harvard, said the university works productively with unions on campus, but he said it believes its relationship with graduate students "is, and should remain, fundamentally an academic relationship."