AUGUSTA — The state Senate Tuesday evening approved major changes to the school consolidation law, allowing local school committees to retain control over their schools in a union form of governance – an amendment that passed in an 18-17 vote after a majority of Democrats decided to go against the administration.

“The point is, it’s agreed to by those communities and is not forced down their throat.” — Sen. Dennis Damon

The amendment, which was pushed hard by school officials on Mount Desert Island, gives communities the option of creating local school boards that have control over local school budgets, teacher salaries and whether a school stays open or closes, Sen. Damon said.

“The point is, it’s agreed to by those communities and is not forced down their throat,” he said.

The local committees would be required to come together in a union, with a regional school union board, which would hire a superintendent, manage central business office functions, oversee transportation and special education and agree on a core curriculum. But local school boards would have the final say on local matters.

On Tuesday, officials from several Mount Desert Island towns, including Brian Hubbell and Paul Murphy of Bar Harbor, and Gail Marshall of Mount Desert, worked the halls at the State House to help pass the amendment.

“We were sweating bullets right down to the roll call,” Mr. Hubbell said. “But in the final tally, Sen. Damon’s effort and commitment paid off.”

Mr. Hubbell added, “It’s not over yet, of course, but the Senate’s passing the Damon amendment is a huge move that will make things better for rural schools all over the state.”

The appeal to home rule and apparent unhappiness among voters in an election year was enough to turn 13 Democrats, who originally supported Gov. John Baldacci’s school consolidation plan. Two significant switch votes were Majority Leader Sen. Libby Mitchell of Kennebec County and Assistant Majority Leader Sen. John Martin of Aroostook County. Senate President Beth Edmonds voted against the amendment.

The amendment will be given a second vote in the Senate on Thursday, and then goes to the House, where it is supported by Majority Leader Hannah Pingree, a North Haven Democrat who also represents parts of Mount Desert Island.

The only people to vote against the governor’s bill last year in the Senate were seven Republicans, five of whom supported the union amendment Tuesday. At the time, Minority Leader Sen. Carol Weston, a Waldo Republican, was the only member of Senate leadership in either party to oppose the governor.

The governor’s plan, which is law today, requires no more than 80 districts statewide, governed by regional school boards. Local school committees can exist, but only in an advisory fashion. The law specifically does not empower local school committees.

The goal of Gov. Baldacci’s plan is to reduce the cost of education at a time when enrollment is declining, but the state’s share of funding for K-12 education is going up. That forces tough decisions between education and health care for the poor and elderly, according to the administration. Education and Health and Human Services combined equal 80 percent of the state budget.

Under Sen. Damon’s amendment, communities could opt to form regional school boards, or go the union route with local school committees.

Education Commissioner Susan Gendron has come out strongly against the union proposal, saying it essentially opens the door to 100 or more school districts on top of the 80 the current law requires.

Asked the day before the vote if the governor would veto an amendment that allows empowered local school committees aligned under a union, Ms. Gendron said Gov. Baldacci has not been that specific yet.

“He has not come right out and said he would veto that,” she said, but added, “He wouldn’t support anything with that size of fiscal note on it.”

In reality there is no firm cost estimate on the amendment yet, but Ms. Gendron said it is expected to be substantial. Local school officials argue the cost would be minimal.

Sen. Peter Mills, a Somerset Republican and a member of the Education Committee, opposed the amendment, saying it undoes all the work that has gone into school consolidation.

“It is tantamount to repeal of that effort,” Sen. Mills said. “It’s basically saying local school committees can hire and fire, and engage in their own contract negotiations. There will be different salary scales. You can even have your own school calendar.”

All of that, Sen. Mills said, flies in the face of finding efficiencies through paring down the number of school districts from the current 290 to around 80.

Sen. Damon argued, however, the union amendment would still push for no more than 80 superintendents, who would manage regional unions of between 1,200 to 2,500 students or more where possible.

The fact that unions would not have to negotiate a single contract for teachers is a plus, he said, because not everyone can afford to pay the high salaries their neighbors might be paying.

“This helps avoid the very real expense of being brought into a unified contract,” Sen. Damon said.