FARMINGTON — Residents will get their last chance tonight to review the 2012-13 budget proposal for Mt. Blue Regional School District 9, which would raise the overall amount district towns pay in school taxes by about $355,000.

District officials will present the $28,907,417 budget proposal at the 7 p.m. meeting in the Mt. Blue High School gymnasium. The spending plan will go to a validation vote Thursday in the district’s 10 towns.

Among the budget proposal highlights is a plan to subcontract the district’s custodial services, which has been at the center of heated negotiations between district officials and the union representing the workers.

School board members voted to seek at least $200,000 in the proposed school budget and each subsequent year.

They also voted to make the budget cuts by subcontracting custodians jobs, unless a new contract was reached with the union.

The subcontracting would affect about 40 union workers, who face either layoffs or the loss of health insurance benefits.

School district officials and union representatives last week failed to agree on a new contract to prevent the subcontracting. District officials plan to move forward with subcontracting some time this summer if a contract isn’t reached in future negotiations.

The budget proposal reallocated most of the projected savings from the subcontracting, going toward two teaching positions and other education services.

About $84,000 of the projected subcontracting savings went to reduce school taxes, Superintendent Michael Cormier said last week.

Cormier has said the budget shortfall is caused by increases in other fixed operational costs, such as fuel and mandated educational programs.

The district also lost federal stimulus money this year that had previously helped absorb some of the costs over the past few years.

School board members are not increasing the budget to pay the annual debt on the construction of W.G. Mallett Elementary School and a new high school complex, Cormier has said.

State subsidies are paying for nearly the entire cost of the projects, which have a combined cost of more than $70 million, he said.

Without the debt payments, the budget proposal is about $1 million more than spending in the current fiscal year.