The nation's largest labor union, the National Education Association, has decided to let its local chapters join the A.F.L.-C.I.O., labor officials said yesterday.
The decision by the association, which represents 2.7 million teachers and administrators and other school employees, will buoy the A.F.L.-C.I.O., which has been reeling because unions that represented nearly one-third of its members have seceded in the last year.
A spokesman for the teachers' union declined to comment on the decision. An official of the labor federation who insisted on anonymity, said its president, John J. Sweeney, and the president of the teachers' union, Reg Weaver, would make their announcement on Monday at the winter meeting of the federation in San Diego.
The move was in part orchestrated by the other large teachers' union, the American Federation of Teachers, which is in the federation and has long had a tense relationship with the N.E.A.
The education association has 13,200 chapters, and officials predicted that over the next five years hundreds of its chapters, perhaps thousands, would affiliate with the federation, which represents nine million workers.
For the federation, the move means more money, members and lobbying muscle. For the teachers' union, it means that the union can use the considerable lobbying power of the federation on issues like vouchers and education financing.
In 1998, the education association rejected a proposal to merge with the American Federation of Teachers, a move that would have made the association part of the umbrella federation.
The A.F.T. was founded as a militant union. The education association long considered itself as a more genteel professional organization. But in the last few decades many of its chapters have acted as unions, negotiating contracts with school boards and cities.