More than a dozen officials from all six Island towns, along with superintendent of schools Dr. Matthew D’Andrea, gathered Wednesday at the regional high school to begin developing an intermunicipal cost-sharing agreement to rebuild or replace the aging school.

With tens of millions of dollars at stake, the tone of the meeting was sober and businesslike as the newly-formed committee took the measure of its task: To convince the Massachusetts School Building Authority that Martha’s Vineyard is ready to collectively shoulder more than 60 per cent of the cost of project that could cost more than $100 million.

“We’re here only to talk about the capital formula for the high school, not the [operational] formula,” said West Tisbury select board chairman Cynthia Mitchell, who will lead the meetings.

Any changes to the formula will require approval from all six towns.

The new capital formula committee is composed of the Island’s six town administrators, accompanied by an elected official from each town, plus Mr. D’Andrea.

Aquinnah finance committee chairman Allen Rugg and select board members Jim Malkin of Chilmark, Arthur Smadbeck of Edgartown, Brian Packish of Oak Bluffs and Jeff Kristal of Tisbury represented their towns at Wednesday’s meeting, gathering at a hollow square of tables in the high school library.

West Tisbury finance director Bruce Stone joined Ms. Mitchell and town administrator Jen Rand at the table.

Citing a legal opinion from attorney Jack Collins, Ms. Mitchell drew a consensus from the group that it is not obliged to follow standard public meeting rules such as posting agendas, keeping minutes and following parliamentary procedures.

But members of the public and press may attend to observe the discussions, committee members agreed.

“I have no problem with people looking over our shoulder. We’re not doing anything in secret,” Mr. Smadbeck said.

Ms. Mitchell also confirmed the priority goal: to secure the MSBA funding, which would reimburse about 38 per cent of most construction expenses.

“In other words, if there’s negotiating to be done and one town needs to give a little . . . the real goal here is to keep the MSBA as part of the equation,” Ms. Mitchell said.

Mr. Smadbeck agreed.

“I see that as absolutely paramount,” he said. “We owe it to the community and we owe it to the children . . . We have to come together.”

The meeting touched on Chilmark’s proposal, aired earlier this year, that the three down-Island towns pay 75 per cent of the project’s cost with the remaining 25 per cent divided among the three up-Island communities.

But no counterproposal emerged during the group’s first hour together, with the sense of the meeting appearing to be that its members have homework to do before they can wade into substantive negotiations.

The West Tisbury delegation distributed a report on the payment in lieu of taxes (PILOT) program in effect for the city of Northampton.

“Were Oak Bluffs wanting to be compensated in some way for the fact that their municipal services are affected [by the high school], that can be done by [PILOT],” Ms. Mitchell said.

Edgartown town administrator James Hagerty distributed a report that included enrollment numbers and projections, fund-allocation formulas for 37 rural and suburban regional school districts in Massachusetts and property valuations for similar homes, one on each of the Edgartown-Oak Bluffs border, with widely differing assessed values.

“This is in here is to demonstrate that equalized valuation is not so equal,” Mr. Hagerty said.

The group agreed to meet weekly, with the goal of arriving at an agreement by mid to late May.

The next meeting is scheduled for 6 p.m. April 28 in the high school library.