WHITEFIELD — A proposed change to the allocation of costs in Regional School Unit 12 would benefit high-valuation towns in the southern part of the district.

Palermo, Somerville and Windsor, on the other hand, would have to contribute significantly more to the district’s budget.

The RSU 12 school board will consider a new local cost allocation at Thursday’s meeting, 6:30 p.m. at Wiscasset Primary School, and all eight towns in the district must approve the plan at referendum or town meeting.

RSU 12 has a $25.1 million budget this year, $13.7 million of which is local contributions from the towns.

When the district consolidated, its budget was built based on each town’s spending on education the previous year. The consolidation plan said the school board could re-evalute the allocation after three years.

Last year, Alna residents petitioned the board to do that. The finance committee has spent the past several months studying examples from other districts and running computer simulations based on various factors.

Wiscasset now pays $4.7 million, 35.1 percent of the local funding for RSU 12. Under the new distribution, the town would pay 31.7 percent — still more than twice as much as any other town.

Alna, Chelsea, Westport Island and Whitefield also would contribute a smaller percentage of the local funding. Palermo, Somerville and Windsor would pay larger portions.

If the new allocation were applied to this year’s budget, Palermo would pay $357,036 more; Somerville $137,321 more; Windsor $425,697 more; and Wiscasset $466,894 less.

The proposal includes a safety net that prevents any town’s contribution from changing more than 5 percent from one year to the next, so the new allocation would be implemented in steps, reaching the final values within five years, said Jerry Nault, a Windsor board member and chairman of the finance committee.

Each town has a state-mandated minimum amount it must contribute to the RSU — based largely on property valuations — for the district to receive state subsidy. For the eight towns in RSU 12, that adds up to about $10.5 million of the $13.7 in local funding this year.

The funding formula that produced the new allocations was applied to the $3.2 million in additional local funding. It incorporates two factors: student count and town population, each weighted at 50 percent.

Some school districts also include property valuation, Nault said, but the finance committee decided not to.

“Some on the committee thought we should put less on valuation because the minimum required amount is largely driven by property valuations,” he said.

It’s hard to predict how the new allocation would affect tax bills, Nault said. The percentage required from each town could change if student counts don’t follow assumptions used in the computer simulation.

In addition, state support for education could rise or fall, so a town that owes a smaller percentage of the budget in 2015 could end up contributing more dollars than it does now.

Several steps will follow Thursday’s school board meeting.

An initial public hearing will take place in the first half of December for board members to hear public input.

The finance committee may change the proposal based on that input, and the board will vote on a final proposal in January, which would then be presented at a second public hearing in late January or early February.

Each town would have to vote on the new allocation by the end of March so that it could be used for next year’s budget.

Wiscasset, the biggest beneficiary under the initial proposal, will vote today in a nonbinding referendum on whether to explore leaving RSU 12.

Wiscasset’s role as the largest source of local funding is one of many issues that town residents have with the RSU, said Judith Colby, chair of the Board of Selectmen; others include questions of local control and educational quality.

“People are wondering, ‘What am I getting for my money?'” Colby said.

A new allocation probably would require less of Wiscasset no matter what the formula, Nault said.

“They were burdened with a lot of historical costs,” he said. “This wasn’t throwing them a bone.”

Susan McMillan — 621-5645

smcmillan@mainetoday.com