WEST WARWICK — The School Committee has exercised its option to let its current teachers contract lapse after three years rather than four, a move that prompted the union to announce that its members would immediately start working to rule — doing only what is strictly required under the contract.

The contract with the West Warwick Teachers Alliance that took effect last Sept. 1 was a four-year agreement — providing annual raises of 3.9 percent — but it includes the proviso that either party could choose, before Sept. 1 of this year, to eliminate the fourth year (ending in 2010) and instead negotiate a fresh agreement.

The School Committee voted unanimously on Tuesday of last week to take that option, Chairman Daniel T. Burns Jr. said.

Given the district’s fiscal straits — it entered the current fiscal year with a budget $1.7 million out of balance — it “would have been fiscally irresponsible to let it go to the fourth year,” Burns said on Tuesday. “I can’t promise you a rose garden if all I’ve got is weeds.”

Yesterday, Donald E. Vanasse, president of the 340-member teachers union, announced its new stance.

“The long and the short of it is that, over time, teachers will not be performing duties that are not part of the school day,” said Vanasse. “The teachers will do what they’ve been contracted to do. They’ll do their jobs and do them well. But they’re not going to do the extras that aren’t required but that they always do anyway.”

That means gradually phasing out participation in programs after school and during the summer, as well as any other volunteer efforts in which teachers normally take part.

At last week’s School Committee meeting, more than 200 teachers showed up to urge the board not to exercise its contract option, Vanasse said.

In July, the school board reconciled its budget, slashing after-school programs and middle school athletics, and laying off a number of teacher assistants. It also proposed cutting transportation spending, reducing the number of substitute teachers and reducing its special-education tuition budget, with the hope that the state Department of Children, Youth and Families cuts down on the number of placements it sends the town.

The cuts were necessary to prepare the district to move ahead with a lawsuit against the town, a provision known as a Caruolo action, which it hopes would garner more money to operate this year. The district also applied for a number of waivers of state mandates from the Department of Education, which were rejected.

The next fiscal year is expected to be even harder. The state-imposed cap on tax-levy increases will tighten, leaving the town with even less money to provide to the district.

With those kinds of cuts, Burns said, it would have been unjustifiable to keep the current teachers contract in force for the full four years. Now, he said, the district can assess its finances when the time comes to decide what it can reasonably offer the teachers.

Burns said he has no qualms about the board’s vote because it was an option available to both parties.

“I don’t know why they’re upset,” Burns said. “Their side could have chosen to opt out if it wasn’t to their benefit.”

For now, the union will wait to see if the board will rescind its vote — an action that would allow the dynamic to return to normal, Vanasse said.

“The union door remains open, but someone has to walk through that door,” Vanasse said.

tbuford@projo.com