ROCKLAND, Maine — City property owners will be paying out nearly an additional $500,000 to cover next year’s proposed school district budget.

Regional School Unit 13 released Wednesday the tax impact from the proposed 2013-12014 budget. The $27,453,548 budget represents a 4 percent increase from the school expenditures approved by voters for 2012-2013.

But because of a graduated shift in the local cost-sharing formula approved by district voters when RSU 13 was formed four years ago, Rockland has seen its share of the budget increase each year.

As a result, Rockland property owners will be asked to pay an additional $490,000 for the next school year if the proposed budget is approved. That increase is the largest by far of any of the six communities that make up RSU 13.

With that increase, Rockland’s total payments to RSU 13 will reach slightly more than $8 million for 2013-2014.

The $490,000 increase would likely boost the city’s tax rate by about 63 cents per $1,000 of valuation. A home assessed at $150,000 would see its taxes increase by nearly $100 from the school budget.

The tax impact information comes as the city administration is preparing the proposed 2013-2014 municipal budget that is expected to be released to the Rockland City Council later this month.

Rockland Manager James Smith said last month that he asked department heads to show him what 10 percent cuts to their departments would look like, although he said at the time that it was early in the budget process. The need for cuts was being considered because of the potential loss of state revenue sharing. Rockland is receiving $729,000 in 2012-2013 from state revenue sharing.

Rockland Mayor William Clayton said he does not want the municipal budget to increase at all.

Clayton said Wednesday that an increase of any kind is never going to be received well by anyone, and that includes those in charge of deliberating over budgets.

“The school board and school officials are in a very tough place, tasked with a fiscal objective while keeping the priority of the students’ safety and education at the forefront,” Clayton said. “Although as the mayor I wish the budget had been kept at least flat, especially since we as a municipality are starting with a 10 percent reduction, I feel the school board has brought forth a reasonable budget. With the recent proposal of further consolidation, which could have resulted in a major savings, I commend the school board for not moving forward with that plan until further discussion is had. Public opinion was heard and eventually agreed with. That is worth the most.”

In RSU 13, Owls Head will see the second largest increase with its share jumping $224,000, which would bring its total payments to the district next year to slightly more than $2.6 million.

Thomaston’s increase is projected at $138,000, bringing its share to nearly $3.4 million.

Cushing will pay an additional $127,000, reaching nearly $2.7 million next year.

St. George’s increase is projected at $102,000, bringing its annual payment to the school district to nearly $4.3 million.

South Thomaston will experience the smallest increase, with its costs expected to rise $94,000, reaching $2.6 million.