CHICAGO (AP) — The Chicago Teachers Union and three teachers who lost their jobs this year have sued the city's school board claiming the practice of "turning around" schools discriminates against black teachers.

The lawsuit was filed Wednesday in federal court in Chicago. The plaintiffs are seeking class-action status.

The teachers — Donald Garrett Jr., Robert Green and Vivonell Brown Jr. — say the practice of firing all the staff at so-called "turnaround" schools has led to a steady decline in black teachers in the school district.

Chicago schools spokeswoman Marielle Sainvilus says that district officials can't comment on the lawsuit. But she says the district "has an obligation to expand high-quality school options ... in every neighborhood."