Santos Crespo, a local president for the DC-37 labor union, on the last day of work for nearly 700 school aides last month.

The union that represents school aides is suing to roll back layoffs of nearly 650 members that took place last month.

Lawyers for District Council 37, which includes school aides and parent coordinators, plan to file a lawsuit over the layoffs on Wednesday, according to a press release the union just sent out.

The suit will argue that the Department of Education acted in bad faith during its negotiations with DC-37 over the jobs, declining to consider other ways to save money or considering whether the City Council and principals might pitch in with their funds. It will also argue that the DOE violated state law by conducting layoffs that disproportionately affected schools with many poor students.

Principals chose to cut school aide positions over the summer as they hammered out slimmed-down budgets for this year, and the layoffs took place in October after charged negotiations between DC-37 and the city failed.

City Council members said they had not gotten enough warning about the layoffs to be able to figure out a way to save the jobs. But city officials pointed out that the budget the council members approved in order to avert teacher layoffs called for other city workers to lose their jobs.

In the union’s press release, Local 372 President Santos Crespo argued — as he had at several protests before the layoffs took place — that the city could have saved a great deal of money by making a cost-cutting deal with DC-37.

“There is no clear monetary justification for the layoffs,” Crespo said in the release. “We want a swift and positive resolution that will get these hard working people back into their jobs.”