The latest squabble in the long and often contentious relationship between regional school district partners Bridgewater and Raynham could land the pair on opposite sides of a court suit before the summer is out.

At issue is the 50-year-old former regional high school on Mount Prospect Street in Bridgewater, which was replaced by a new facility about six years ago. Bridgewater converted the old building to a middle school for the town.

Since Raynham students don’t attend classes at the former high school, Raynham has expected its regional partner to buy out its interest in the building.

Bridgewater has been resistant.

After failed negotiations that span several years, Raynham has decided to take Bridgewater to court.

“We have thoroughly researched this and have extensive documentation,” said Raynham Selectman Joseph Pacheco of material being prepared for the court case. While he wouldn’t say how much Raynham wants for the old building, Pacheco said, “It adequately reflects our stake.”

According to Bridgewater’s assessors, the former high school property is currently valued at $23.1 million.

Calculations done by the regional district in 2002, when plans for the new high school were being formalized, set a potential buyout payment to Raynham for the old high school at about $7 million. At the time, officials thought the state might cover some of the amount, but have since learned the state will contribute nothing.

Raynham’s percentage share in the school district is one-third to Bridgewater’s two-thirds, based on student population.

Bridgewater Town Councilor Michael Berolini argues the amount should be calculated not on present value, but on what the school cost to build originally. He added the state picked up a large percentage of the cost.

“Raynham’s initial cost was $600,000 or $700,000,” Berolini said. “The building is almost 50 years old, and you have to factor that in. You also have to consider Raynham utilized it for 40 or 50 years.”

Berolini conceded Raynham doesn’t agree with Bridgewater’s opinion of what’s owed. “We’re millions of dollars apart,” he said.

Bridgewater made an offer to Raynham in January that included “some money along with other items,” Berolini said. Included in the deal was the promise of a future payment were Bridgewater to sell the building.

Pacheco called the January offer unacceptable, falling short of his town’s expectation “by a substantial amount.”

The state Department of Elementary and Secondary Education has become involved in the issue, even though the agency has no authority to settle squabbles over school buildings. Deputy Commissioner Jeff Wulfson attended the final session between the two towns in January, hoping to facilitate a resolution. But both sides left the table that day and haven’t returned.

Wulfson called the situation unusual.

“There have certainly been realignments of regional school systems that involve a reassignment of buildings, but I don’t recall one this contentious,” he said.

Raynham has instructed its attorney, Fernand Dupere, to prepare the lawsuit against Bridgewater. Dupere said he will probably be ready for court by summer’s end, should the stalemate continue.

Raynham officials selected Dupere because of his experience with regional school realignments. The lawyer was involved in Pembroke’s departure from the Silver Lake Regional School District some years ago. That split required a distribution of assets along with building buyouts, which Dupere said was done without the need for litigation.

“I have not had to go to court on the sale of school buildings or the transfer of assets in the past,” Dupere said. “And I don’t know anyone who has.”

Raynham assessor Gordon Luciano, who has been involved in buyout talks since 2003, first as a selectman and later as a Bridgewater-Raynham Regional School Committee member and assessor, said Bridgewater has argued the regional district still uses the building, currently housing its administrative offices there. He said the regional administration also operated out of a Raynham school building for about a dozen years before moving to Bridgewater, at no charge to the district.

“Raynham patiently waited for Bridgewater to get its house in order and properly fund the school district, and Raynham has been patient about this, too,” Luciano said. “But it’s frustrating for officials that we haven’t reached any resolution yet, and it’s deeply frustrating for Raynham residents that everything we do with Bridgewater, every budget, every item, is a struggle.”

Berolini said he would be willing to return to negotiations but believed it would be fruitless. “If we were closer, I’d say maybe we could reach some agreement, but we’re millions of dollars apart,” he said.

The Bridgewater councilor said some in town believe Bridgewater shouldn’t have to pay anything for the school, while others believe “a reasonable payment” is owed.

“We don’t have all this money set aside,” Berolini said of the town’s offers for a buyout. “I offered what I think is fair, and I don’t think I could get the Bridgewater councilors to go any higher. I was getting pushed back by some on the offer I made.”