Teachers in the 12,000-student district have been working without a contract since June 30, 2012.
The union, which represents more than 900 educators, said a fair contract would include cost-of-living adjustments and a raise not offset by benefit payments.
The three-year proposal it turned down last month called for teachers to get no raise in the first year, a 1.7 percent increase in the second, and 3.1 percent in the third. It also called for teachers to pay 12 percent of benefit costs in the third year.
The board said it had agreed to concessions, such as increasing reimbursements to teachers for taking graduate courses and delaying benefit cost sharing, but said additional costs could hurt the district.
"They have been trying to negotiate through press releases, and that is in the broadest sense of the word negotiate," said Chris Bruno, a Henderson High School teacher and union negotiator.
The school board has been willing to talk, said its president, Vince Murphy.
"We negotiated with the union leadership and we had a tentative agreement, so we're not sure what the union members want," Murphy said.
The school board's chief negotiator, Jeff Sultanik, said he told the union to try working with a state mediator.
"Ironically, this is the first time I think we agree," Bruno said. "We see no reason to go back to the table to talk about cuts that are going to hurt our kids."
The school board election on Nov. 5 is giving some in the union leadership hope that negotiations can succeed if new members are elected.