The forum, sponsored by the League of Towns, is the latest in a longstanding debate about the 40-year-old funding formula. The cost of funding the high school falls on the shoulders of the four island towns: Bar Harbor, Mount Desert, Tremont and Southwest Harbor. Mount Desert selectmen and some of the town’s residents feel strongly that the formula is inequitable.

“We’ve been talking about it being unfair for decades. After 30 years, things should have changed,” said selectman Chuck Bucklin.

Education officials in the three other member towns find no fault with the formula, based on 67 percent valuation and 33 percent enrollment. The formula, voted in by all four member towns in 1965, penalizes towns with high property valuations and low enrollment, say its critics. Those critics tend to analyze the formula’s fairness based on each town’s cost per student.

There are two ways of looking at the funding formula, said School Union 98 superintendent Rob Liebow; you can evaluate its fairness based on taxpayers ability to pay, or you can focus purely on a per-pupil cost calculation.

Although Mount Desert selectmen would like to see a formula based on 100 percent enrollment, they are open to compromise. “Let’s make a deal,” said selectman Patrick Smallidge.

The forum is not the first organized effort to discuss the funding formula. Two years ago, the high school committee formed a subcommittee charged with evaluating the formula’s fairness. Mount Desert resident Gail Marshall was chairman of the subcommittee. Ms. Marshall, now the chairman of the high school committee, supports the current formula. Under the committee’s authority, Mr. Liebow worked with Mount Desert tax assessor John Brushwein to analyze the formula based on taxpayers’ ability to pay.

The basic premise of that thinking is inherently flawed, say funding formula critics.

The committee found that the formula was fair and made no recommendation regarding the formula’s revision.

Mr. Smallidge, the Mount Desert selectmen’s chosen spokesperson on the issue, said he would be open to discussing any possible change to the current formula. If enrollment in Mount Desert continues to decline and property valuations continue to go up, the cost per student in Mount Desert could reach $35,000 in the next six years, he said. “The figures are absolutely horrifying. We’re paying double for the same service now.”

Because Bar Harbor has more students who attend the high school, the town’s average per pupil cost is about $10,000, while Mount Desert’s is closer to $20,000.

Based on a per-pupil calculation, the formula is not equitable. When evaluating the funding formula based on percentage of taxes paid by like-valued property owners, the formula is equitable.

Under the formula, a property owner in Mount Desert with a home worth $336,000 will pay about $550 in taxes toward the cost of education, while a property owner in Bar Harbor with a home of the same value will pay about $650. As home values go up, Mount Desert property owners continue to pay slightly less than Bar Harbor property owners with homes of the same value.

It is the responsibility of all island towns to share the cost of educating students, “regardless of whether they have students in school or whether they are a year-round or summer resident,” said Mr. Liebow.

Across the state, a multitude of funding formulas exist. Some are based purely on enrollment, some purely on valuation, while others employ some variation of a combination of the two. As a change to the formula would need a formal vote from each member town, this forum will be for discussion only.

Neutral party Reverend Ted Hoskins of Blue Hill is set to moderate the Dec. 4 session in the high school’s Demas-Higgins Theater at 7 p.m. An online discussion forum on the topic is available at http://forum.mdischools.net.