A BID BY NEW BEDFORD OFFICIALS  to peaceably resolve a dispute with a local charter school hit a potential roadblock on Tuesday, as the Massachusetts Teachers Association said a key element of the deal is illegal.

The deal calls for the Alma del Mar Charter School to add 450 seats in New Bedford rather than the 1,188 it had originally sought. In return, the city agreed to turn over to the charter school a shuttered school building, the former Horatio A. Kempton Elementary School, at no cost. The arrangement, brokered by state Education Commissioner Jeff Riley, is seen as a possible way around divisive charter expansion battles.

The teachers association, however, said New Bedford cannot simply give away its empty school. The association, in a letter to Mayor Jon Mitchell, said the transfer appears to violate three laws – the state’s Uniform Procurement Act, a law covering the disposal of surplus property, and the so-called anti-aid amendment of the state constitution.

“The unorthodox deal is clearly not based on a unique situation necessary to promote public education, as that can be done without giving away property,” the teachers association said in a press release.

New Bedford City Solicitor Mikaela McDermott dismissed the MTA’s assertions. “The MTA’s arguments have been reviewed by the city solicitor’s office and the School Committee’s counsel.  All  attorneys disagree with the MTA’s assertions of violations of state law and believe that the MTA is simply wrong,” McDermott said.

Merrie Najimy, president of the teachers association, said in a statement that the deal between New Bedford and Alma del Mar is a prototype for similar deals across the state.

“This is clear a test case promoted by privatizers bent on expanding charter school enrollment after voters rejected their arguments at the ballot box in 2016,” said Najimy, whose organization led the fight against the charter expansion ballot proposal. “First the charter operators want to drain massive amounts of public funds from public schools – and now they want to make a grab for public land.”

Mitchell is hardly someone who would be called a privatizer. He originally opposed the charter expansion, and fought hard to stop it. But, at the urging of Riley, he agreed to a deal with Alma del Mar because he had little leverage to stop an expansion under state law.

The teachers association raised its legal concerns about the disposal of the Kempton school as state education officials are preparing legislation that would need to pass on Beacon Hill before the deal can proceed.

One of the key concessions in the agreement between New Bedford and Alma del Mar is that the charter’s new K-8 school will operate like a neighborhood school – taking students only from the surrounding neighborhood and not drawing from the entire city, as current state law allows.

A memorandum of understanding signed by New Bedford officials, Alma del Mar executives, and Riley indicates the pace of action is quickening. New Bedford is expected to draw the neighborhood boundary for the new school and provide a list of all students in the area to Alma del Mar by April 5, paving the way for enrollment for the 2019-2020 school year. Enrollment will start at 200 students the first year and grow to 450 in year four.

According to the memorandum of understanding, New Bedford will assign neighborhood students to the new school up to the target levels. Once those targets are reached, the enrollment process will stop. The memorandum of understanding says Alma del Mar can but doesn’t have to accept students beyond the target level and the city shall not provide tuition payments to Alma del Mar above the target level.

Under the terms of the memorandum of understanding, New Bedford and Alma del Mar will work to resolve any differences that arise. But if the two sides are at loggerheads, they can present their case to Riley, who will make the final decision.