TIVERTON — The teachers’ union filed an unfair labor practice charge against the School Committee yesterday, maintaining that the committee has bargained in bad faith by failing to send appoint a negotiator authorized to reach a tentative agreement.

The teachers’ contract expired yesterday, and the union membership will meet after school today to consider its next steps.

Union spokesman Patrick Crowley said last night that union filed the complaint with the state Labor Relations Board under a provision of the law that refers to a refusal to bargain collectively.

Crowley, deputy executive director of the union’s state affiliate, the National Education Association-Rhode Island, said decisions of the labor relations board have cited failure to invest negotiators sufficient authority at the table as an example of bad-faith bargaining.

The School Committee’s chief negotiator, Schools Supt. William J. Rearick, must report back to the committee with any offer made by the union, the National Education Association-Tiverton.

Rearick said last night that practice is no different than the president and vice-president of the union reporting back to their full negotiating team on any offer made by the School Committee.

Rearick said he understands that any agreement made by the union president, Amy Mullen, or the vice president, Kristen Destremps, can be overruled by the union’s full negotiating team.

“There are other districts where the superintendent has negotiated” in the same fashion as he has “and nobody filed an unfair labor practice,” Rearick said.

Meanwhile, Crowley released a copy of a memo Rearick sent to teachers Tuesday in which he apologized for telling them to “sit down and shut up” at a district-wide orientation meeting in the high school auditorium earlier in the day.

“My intention was to get the meeting started in a timely manner, in retrospect I should have chosen my words more carefully,” Rearick wrote.

“I want to take this opportunity to apologize to anyone I may have offended,” the superintendent concluded.

Last night, Rearick said that he had tried twice, without success, to call the meeting to order.

His third attempt “wasn’t meant to be disrespectful,” he said. “It was meant to get their attention.”

After the union negotiating team told him later in the morning that some teachers had felt insulted, he decided that the memo was the only way he could “get the word out” that he hadn’t intended to offend anyone.

Rearick said he was “disappointed that they would use this as part of a negotiating tactic.

“The School Committee and myself have been pretty up front” with the teachers’ union, he said. “We’ve dealt with them in a professional manner.”

Rearick accused the union of “resorting to various tactics” to shift attention away from its health-care plan, which he contended will not live up to a claim to save the district $186,000 in the first year. No cost projections have been submitted for the second and third years, he said.

The union says it is the School Committee that has not done the math correctly.

gmacris@projo.com