Graduate teaching assistants at private universities can't form unions because they are students, not employees, a Republican-controlled federal labor board ruled, reversing a Clinton-era decision.

The National Labor Relations Board (search), led by three Republicans appointed by President Bush, ruled that about 450 graduate teaching and research assistants at Brown University in Providence, R.I., could not be represented by the United Auto Workers (search).

The two Democrats on the five-member panel opposed the decision, which does not affect public universities and colleges. The ruling, overturning a 2000 decision, was made public Thursday.

Graduate teaching assistants criticized the decision.

"We intend to continue our struggle," said Lauren Nauta, a graduate teaching assistant at the University of Pennsylvania, a private school in Philadelphia. Teaching assistants are workers who deserve to "have a voice in our working conditions and our compensation," said Nauta, who is organizing director for the American Federation of Teachers' (search) campus unionization efforts.

James Shaw, a graduate student at the public University of Massachusetts at Amherst, has been involved in organizing campaigns on other campuses, including Brown.

"People are trying to raise families, get their health care needs covered," Shaw said. "The needs of a graduate employee are the same as for any other worker."

But the labor board disagreed.

"Because they are first and foremost students, and their status as a graduate student assistant is contingent on their continued enrollment as students, we find that they are primarily students," the decision said.

Brown's provost, Robert Zimmer, said the new ruling "correctly recognizes that a graduate student's experience is a mentoring relationship between faculty and students, and that it's not appropriate for collective bargaining."

Alan Reuther, UAW's legislative director in Washington, said, "We strongly disagree with it and we think it reflects this administration's anti-labor orientation."

The decision overturns the board's unanimous ruling in 2000, which let 1,500 graduate teaching assistants join a union at New York University, the first private school where that happened.

The Clinton-era ruling by two Democrats and a Republican — there were two board vacancies — said graduate students who work and receive compensation as researchers and teaching assistants at private universities have the same rights as other workers to form unions and negotiate working conditions.

But the current board now says that decision was wrong because it reversed more than 25 years of precedent.

"In our decision today, we return to the board's pre-NYU precedent that graduate student assistants are not statutory employees," the ruling said.

NYU, in a statement Thursday, said it was gratified by the decision and noted that the contract it negotiated with graduate teaching assistants is up for renewal in a year. "The university will not make any decisions about its next steps until it has an opportunity to review today's ruling carefully," the statement said.

Universities increasingly are replacing tenured classroom teachers with part-time faculty and graduate students. Unions, trying to reinvigorate the labor movement, have moved in to help boost membership.

"This ruling is outrageous," said Nat LaCour, AFT executive vice president, eliciting loud boos as he told members at the union's convention of the decision. "This must change."

The union represents 150,000 faculty members, including 12,000 graduate teaching assistants, at private and public colleges and universities.

The NLRB, a government agency, deals with private employers and has no jurisdiction over public universities and colleges, which are governed by state laws. Those laws vary on whether graduate teaching assistants can unionize.