SEEKONK — The School Committee on Friday approved new three-year contracts with the teachers union and four other bargaining units and said that a Special Town Meeting would be necessary to seek financing for this year’s 3.5-percent salary increases.

In the second and third years of the contracts, members of the Seekonk Educators Association and the unions representing administrative secretaries, custodians and maintenance personnel, school bus drivers and crossing guards will earn 2-percent raises, plus another 2-percent pay hike after their 92nd day worked — averaging out to about a 3.1-percent increase for the final two years of the bargaining agreements, schools Supt. Emile Chevrette said yesterday.

The contracts for all unionized school district employees will cost just under $2.1 million over three years, Chevrette said, with $557,000 needed in this fiscal year.

But the School Department’s current-year budget does not include money for pay raises. So the School Committee is recommending a Special Town Meeting to put the spending request before the voters. The contracts are predicated on voters’ approval; if they reject the additional money, the school district will have to renegotiate.

A petition signed by 200 certified Seekonk voters is necessary to request a Special Town Meeting. Once the names are certified as registered voters, the Board of Selectmen has to schedule a town meeting to take place within 45 days.

The Special Town Meeting would be in addition to the annual fall Town Meeting, tentatively scheduled for Nov. 17.

Town officials have warned that the schools’ salary hikes will dramatically impact the town’s finances and could have a domino effect. The town is now in contract talks with its seven municipal unions — three of those deliberations are now in arbitration — and it would likely be forced to provide the same raises to those unions as the school system gives its teachers.

The town has targeted $1.2 million, over three years, as the figure it could afford to spend on all bargaining agreements. Any municipal or school salary raises would have to be funded through “free cash,” leftover money that was budgeted but unspent last fiscal year, officials have said. If there’s not enough money, staff cuts are likely on the municipal side, the selectmen have said.

Chevrette said the School Department has returned $500,000 to the town in the last two fiscal years in money it saved in its operating budget. Chevrette said town officials have accepted the money with the understanding that it would be later used to help pay for school-side salary increases.

School Committee member Bill Barker and Town Administrator Michael J. Carroll — who sits as a member of the negotiating team on school contracts — voted against the agreements at the committee meeting Friday night. (Chairwoman Marjorie Bradley abstained from the vote on the teachers contract because her daughter is a Seekonk teacher. Members John Bilodeau and Fran Creamer abstained from the vote on the salaries for athletic coaches because they have relatives on the soccer team’s coaching staff.)

The new teachers contract phases out a six-year-old provision that allowed the children of school employees who live outside Seekonk to attend Seekonk schools for free. The contract adds two unpaid professional development days for teachers for which they can earn two compensatory days off, and formalizes the mentoring program for new teachers. It also raises longevity bonuses by 4 percent. Teachers will continue to pay 25 percent of their health-care costs.

The School Committee at its meeting Friday night also approved pay raises of 37 cents and $3.30 an hour for substitute custodians and substitute bus drivers, respectively.

The school district must still approve contracts with clerical staff, central office administrators and school principals.

mwims@projo.com