While town and school officials up-Island continue their years-long debate over the fairness of their regional school district, the Massachusetts department of education is preparing to enforce statewide changes that could dramatically alter not only up-Island district finances, but also how every Vineyard town pays for the regional high school.

State education officials are set to adopt in December amendments to their regulations that would require regional school districts throughout the commonwealth to use a wealth-based formula as the default way to divvy up school finances. The changes would, in effect, turn on their head the existing intergovernmental agreements that formed the two regional school districts on the Vineyard.

Instead of apportioning regional school costs based on enrollment - how many students each town has in the district - the budget would be divided according to a town's ability to pay. The change reflects the state's philosophy on public education, codified in a 1993 state law, that wealthier towns should pay a larger share of education costs than less affluent ones.

The alternative funding arrangement was always intended to apply to regional school districts, and if formally adopted by the state board of education this winter, it will be enforced for the first time during the upcoming budget cycle. The new formulas would go before Island voters at their annual town meetings this spring.

The regulations would require every town within a regional district to agree each year to use the pre-existing enrollment formula, while the state's wealth-based formula - which incorporates property values and income levels - would only require approval from two-thirds of the member towns. Because at least one Island town stands to benefit financially from the state formula, it may become difficult to receive unanimous support for the existing regional agreements.

Island school administrators have not yet calculated how the wealth-based formula would impact each town's share of the Martha's Vineyard Regional High School District budget, but they intend to have those numbers available by the end of September.

Some school officials are concerned that, because of the funding changes, the high school might be unwillingly drawn into the fray that has ensnared other regional districts throughout the commonwealth. Though the subject of bitter debate on the Island during its creation in late 1950s, the regional high school district in recent years has been relatively free from the conflict and inter-town quarrels that have plagued the Up-Island Regional School District.

High school committee chairman Susan Parker noted this week that individual town assessments already see significant swings from year-to-year based on enrollment shifts at the high school, and she suggested that the new wealth formula would simply be another way for the numbers to change. She said she expects that Island voters will continue the goodwill that they have traditionally offered the high school.

"The Vineyard is proud of our high school, and there has always been a collegial feeling among the towns when it comes to support," Mrs. Parker said. "I think people should be aware [of the possible funding changes], but not concerned."

Up-Island, where relations among district towns are strained, the changes are likely to see more political fallout. School administrators have calculated that, if the state's wealth-based formula were in place for the current year's budget, Aquinnah taxpayers would have saved more than $90,000, while West Tisbury would have paid an extra $70,000, and Chilmark an additional $25,000.

If Aquinnah opts to go with the state formula, it could alienate some voters in West Tisbury, where the finance committee has for years argued that the town shoulders an unfair share of the regional budget.

Some town officials in Aquinnah are embracing the state formula, and selectmen plan to hold a public hearing with school officials in mid-September to ask whether, regardless of the state regulations, taxpayers want them to pursue the wealth-based formula for the up-Island district. Under existing state law, Aquinnah voters already have the ability to unilaterally shift district funding from the existing regional agreement to the state formula.

Though not outwardly endorsing the change, Aquinnah selectman Camille Rose said she thinks voters deserve the opportunity to switch formulas. She noted that the town is in a unique position because of the large number of school children who live on tax-exempt tribal land, and that $90,000 is a significant amount of money. Though only about one per cent of the $7.2 million district budget, the $90,000 difference would decrease Aquinnah's share by roughly 14 per cent.

"This provision was created for communities exactly like ours," Ms. Rose said.

The state's highest court said roughly the same thing eight months ago, when it ruled in a case involving the oldest regional school district in the state. The Massachussetts Supreme Judicial Court in its unanimous December 2005 decision upheld the right of the small town of Rutland in the Wachusett Regional School District to pay less per student than the larger town of Holden, which brought the suit.

Chief Justice Margaret H. Marshall, who is a seasonal resident of West Tisbury, wrote in her ruling that state oversight regarding the wealth-based formula serves "to ensure compliance with applicable law and to protect minority towns from overreaching by the majority."

The state legislature, in its Education Reform Act of 1993, established a new system of public school finance in the commonwealth as a way to level the playing field between communities of different means. The law was intended to supersede existing regional school agreements, but that aspect went unnoticed on the Vineyard, as well as in other communities, because it was not strictly enforced.

The state historically promoted regional school systems as a way to help smaller communities that could not afford to provide the same level of educational opportunities on their own. But regional incentives have decreased along with state funds in recent years, prompting struggling towns in regional districts to take note of the wealth-based formula.

With such debates playing out in communities across the commonwealth, the department of education this year decided to clearly specify the existing state laws within its own regulations. Jeffrey Wulfson, an associate commissioner of the education department, acknowledged this week that the existing laws were relatively convoluted, and said that the amendments are intended to clarify the issue. The board of education is accepting comments on the proposed regulations through Oct. 27.

The West Tisbury finance committee is set to meet with town selectmen on Sept. 12 to discuss the possible changes. Committee member Richard Knabel said this week that, though he could not speak for the entire board, he believes the wealth-based formula might prompt another attempt by the town to withdraw from the regional district. He called the state regulations hostile to regionalization.

"It will change the entire equation for the region, and the reasoning of having all three towns together," Mr. Knabel said. "In our case, one town is going to tell the other two what their budget is going to be. And that would be an end to our regional agreement."