Gloucester may have to decide whether to join a new regional vocational high school sooner than expected.

Regional school officials want to change state law to move up by three years the deadline for communities to join a proposed $130 million school, according to Gloucester School Committee member Melissa Teixeira, the city's representative on the North Shore Technical High School Committee.

Joseph Parisi III, a member of the board overseeing plans for the new school and merger of North Shore Tech in Middleton with Essex Agricultural and Technical High School on its Danvers campus, told city councilors this week the move was necessary.

"We need to know what size school to build," Parisi said. "We can't wait until months before school opens to know what size to build for members."

Mayor Carolyn Kirk has recommended putting off a membership commitment by the city while studying the feasibility of expanding the Gloucester High School vocational program. That idea was based on the understanding that state law gave the city until the summer before the school opens — expected to be 2013 — to join.

The expedited deadline could be as early as next spring, Teixeira said yesterday.

The exact mechanism that would be used to change the law and move up the deadline is unclear, but Council President Bruce Tobey noted that support for the school regionally and at the state level gave regional officials a lot of options.

Parisi and George Harvey of Essex, chairman of the North Shore Tech School Committee, could not be reached yesterday; North Shore Tech Superintendent Amelia O'Malley and Essex Aggie Superintendent Roger Bourgeois did not return phone calls.

Debate over joining the new merged vocational school has become a rending, emotional issue in Gloucester, where the in-house vocational program has deep roots but budget pressure has taken its toll on the entire public school system.

Gloucester's share of the debt service for the new building is estimated at $2.7 million, and additional students attending the new school are expected to drive up annual tuition costs.

As regional planners have sought commitments from member communities, Gloucester has shown the most reluctance to join the expanded district, and many here this week viewed the plan to change the deadline as an act of retribution.

"If that is their tactic, it is one more reason not to join," Kirk said. "We are making an honest attempt to figure out what is best for our district. We can't afford to do everything for everybody."

"It seems like rules are being shifted because of us and I am not happy about that," said City Councilor Jason Grow.

The state is committing just under $100 million toward the construction of the new school, which would be on the Essex Aggie campus in Danvers, leaving the 17 member communities to pick up the remaining $31 million.

Peabody City Council voted to join the new regional school district on Thursday night.

Whether Gloucester joins or not, it appears certain the new school will be built. The only remaining question is how large it will be. Plans call for an enrollment of 1,440 students, but regional officials have said that, if Gloucester bows out of the project, the building could be downsized.

The biggest player in deciding what form the school takes is likely to be the Massachusetts School Building Authority, which has contributed $77.5 million to the project.

Last month, MSBA director Katherine Craven told city officials that, if Gloucester puts off a decision on joining, it would add a layer of uncertainty to the project. But she did not say such a move would break the project or prevent Gloucester from joining in the future.

Both North Shore Tech and Essex Aggie have sizable waiting lists and would probably fill up at the current size even if Gloucester pulls out. Planners would have to decide whether they wanted to save money on construction and keep the same waiting list or continue with the building as planned, Craven said.

The Gloucester School Committee has so far only voted to pledge support for continuing the Gloucester High School's vocational programs.

On Thursday, the School Committee's Building and Finance Subcommittee recommended joining the regional school as long as the cost of the debt service is not transferred to the school budget. It recommended putting off a decision as long as possible.

The full School Committee is scheduled to take up the issue Monday, but because some members may not be able to attend, and may put action on the issue off until Nov. 30, Chairman Greg Verga said yesterday.

Patrick Anderson can be reached at 978-283-7000, x3455, or via e-mail at panderson@gloucestetimes.com