The Cranston School Committee Tuesday night ratified a new teachers union contract that will save taxpayers millions of dollars over the next three years by increasing teachers’ contributions to their health-insurance premiums.

The net savings, however, will be significantly offset over the next three years by higher salary and pension costs.

Teachers will pay 15 percent of the cost of their premiums, up from the current 5 percent. The contribution will increase to 17 percent in 2011-12.

For a family plan, the contribution next year will triple, to $2,758, up from the $919 this year, according to Raymond Votto, the School Department’s chief operating officer. The cost of an individual plan next year will rise to $1,076, up from the current $325, he said.

“I think people are resigned to the fact that health care is very expensive and this is a necessary evil to balance the budget and move forward,” the Cranston Teachers Alliance president, Frank Flynn, said Wednesday. “People are aware of the difficult financial situation the district is in. This allowed flexibility to avoid layoffs and [enabled the district] to recall people from layoffs and save programs.”

In addition to paying more for their Blue Cross Healthmate Coast-to-Coast coverage, Flynn said, teachers also agreed to “very modest” pay raises.

For taxpayers, the biggest cost-savings –– $5.4 million over three years –– will come from higher employee contributions for health insurance, Votto said.

But the $5.4 million –– along with additional cost-savings from measures such as schedule changes in the middle and high schools –– will be offset by higher costs for salaries and pensions.

School officials project a net cost-savings over the next three years of $1.8 million.

Teachers at the top salary step –– about 59 percent of the district’s 975 teachers –– next year will get a 1-percent raise, to $72,088, according to Votto. During the following two years, he said, all teachers will receive pay increases of 2.25 percent.

The pay raises are on top of annual step increases for the 41 percent of teachers who are not already at the top of the salary scale.

A School Committee vote on the contract, which was ratified by the teachers’ union two weeks ago, was originally scheduled for June 22 but had to be postponed when school officials learned they had neglected to post the contract on the district’s Web site, as required by city ordinance, in advance of the vote.

The seven-member committee voted after “very little discussion” to unanimously approve the contract, said Votto.

larditi@projo.com