Video by Donna Eyestone.

Scores of teachers and their supporters stormed City Hall on Tuesday night to demand a new contract from Alameda school district leaders, following all-night settlement talks that ended without a deal being reached.

“We are here tonight because it is time to settle a fair contract,” Alameda Education Association president Gray Harris told the school board before a loud, angry crowd who cheered her with a standing ovation. Harris said the district and its teachers’ union have held 23 bargaining sessions over the past 10 months without reaching a deal.

Teachers from Alameda and other cities, along with members of a host of other unions, packed the plaza in front of City Hall during a pre-meeting rally. The group then marched up the City Hall steps and into council chambers, where they chanted slogans and handed members of the school board postcards demanding a contract.

The raucous crowd cheered Trustees Barbara Kahn and Trish Herrera Spencer, who the union supported for board seats in November, as they were introduced, along with about a half-dozen speakers who supported them.

Superintendent Kirsten Vital told The Alamedan that the district and the union are slated to meet with a state mediator on Monday to discuss contract articles that remain open. The teachers’ union had asked a state board to declare an impasse in negotiations over pay, a move Vital said put all of the open contract articles into mediation.

“We are working really hard to try to resolve this contract as quickly as possible,” Vital said, a comment that drew heckling from the crowd.

Neither Vital nor Harris would comment on specifics of what was discussed during Monday’s all-night negotiations.

“I can’t talk about any confidential settlement talks,” Vital said Tuesday.

The union asked the state Public Employment Relations Board to declare a negotiating impasse on February 8, after district leaders offered a 2.5 percent raise. The union had sought a 4.5 percent raise.

Union leaders said the district has $21 million in reserve and fund balance; they think the school district has more than enough money to provide the raises they’re seeking. But district leaders have said they face future funding challenges that include a potential court judgment requiring them to pay back up to $7.4 million in taxes they collected under Measure H, a 2008 parcel tax.

An official with the Alameda County Office of Education said the district will need to come up a with a plan to pay the money back if the courts ultimately decide the district exceeded its taxing authority by charging homeowners and commercial property owners different rates, and if the district fails to get relief from a bill proposed by Assemblyman Rob Bonta that would allow school districts to levy the “split-roll” taxes and would apply to Alameda Unified retroactively.

“We are asking the board to adopt some type of contingency plan that accounts for the fact that it is a real possibility, and an unfortunate possibility, that they may have to refund taxes as a result of the lawsuit,” said Damon R. Smith, the Alameda County Office of Education’s assistant superintendent for business services.

He said it would be up to the board to decide how much to set aside.

“It needs to be something you and the district feel would protect the district and prevent it from going into receivership,” Smith said.

The contract demand came as administrators talked to the board about boosting teacher collaboration in the district’s schools, something they had proposed in an earlier contract offer but retracted when union leaders said it was unfair for the district tie additional work to raises they think are overdue. District leaders had proposed giving teachers an annual $1,000 bonus for participating in a two-year pilot of a Professional Learning Communities approach that would seek to boost student achievement – and particularly, achievement for struggling students – through collaborative planning and assessment.

Assistant Superintendent Sean McPhetridge said some form of collaboration is already taking place at many of the district’s schools – collaboration that requires a contract waiver from the union at each school. The district’s earlier pay proposal would have eliminated the need for the waivers and extended a uniform collaboration approach across Alameda Unified’s schools.

McPhetridge said collaboration will be particularly important as the district implements new learning standards that are being put in place at school districts in almost every state.

“What I’ve come to recognize, and what most of my colleagues have come to recognize, is that we do this better together than we do it alone,” he said.

Related: State declares impasse in teacher pay dispute