Urban Prep Charter Academy for Young Men illegally fired 15 teachers in the wake of June 2015 elections to unionize the all-boys charter schools, the National Labor Relations Board has said, and now the school is on the hook for more than $260,000.

Settlement papers signed Monday show that Urban Prep agreed to hire back all the fired teachers and pay out some $261,000 in back pay plus interest.

Just two of them accepted jobs, according to Brian Harris, president of Chicago Alliance of Charter Teachers and Staff, the union that represents Chicago’s charter school teachers, and both were sent to different campuses than where they previously worked. They were reinstated Monday.

The labor board said in a complaint that one of those teachers, Mathias Muschal, was fired specifically in retaliation for his participation and leadership in efforts to unionize teachers at the charter high schools. Most of the others — but not quite all — were involved in union efforts, Harris said.

In a statement, the charter chain denied any wrongdoing and said it decided to settle rather than go to trial “in the best interest of our students and schools to avoid additional disruption and longer-term expenses that would be certain if these matters were litigated to conclusion.”

“Urban Prep has always respected teachers’ right to organize, and as such, would never dismiss any teacher because of his or her organizing activity,” chief operations officer Evan Lewis wrote.

Lewis also noted that the union initially alleged that three of its employees were dismissed in retaliation for their union activities but for two of them, “the Board correctly determined that there was insufficient evidence to support those allegations.”

According to settlement documents, Urban Prep agreed that in the future it will not fire anyone “because you engage in protected concerted union activity or because of your union membership or support,” and that it will provide notice of major employment changes to the union before taking action.

Meanwhile, the ACTS and Urban Prep continue to negotiate their first teacher contract.

The charter chain had argued to the labor board that seven staffers were let go because the schools restructured its curriculum and eliminated several courses and the other eight were let go for performance reasons.

Harris said Urban Prep fought efforts to organize last spring at its three campuses, making staffers sit through anti-union slide presentations.

Those let go about two weeks after voting to form a union took an unfair labor practices case to the National Labor Relations Board, and protested at a board meeting of Urban Prep.

Chicago’s charter schools have been slowly organizing, with 32 of Chicago’s approximately 130 campuses now represented by ACTS, which is separate from the Chicago Teachers Union.

Mayor Rahm Emanuel, who often appears at Urban Prep events, even threw his support behind the teachers in February, as he struggled to defeat pro-labor challenger Jesus “Chuy” Garcia, saying through a campaign spokesman that “Just as he was supportive when the teachers at UNO and other charter schools decided to organize with a union, Mayor Emanuel fully believes in the fundamental right of workers to bargain collectively.”

Harris said that support vanished once Emanuel defeated Garcia in an April runoff.

“Rahm Emaunel said he was going to support these teachers in February‚ and then didn’t want anything to do with us after the election,” he said.

A mayoral spokeswoman would not say what Emanuel did to show that support, just that “The mayor has and continues to support the right of individuals to bargain collectively.”