National education officials are investigating how Chicago Public Schools has handled closing schools in recent years.

A spokesman for the U.S. Department of Education confirmed Tuesday that CPS is one of six urban school districts being investigated by the department’s Office of Civil Rights. School districts in New York City, Philadelphia, Newark, Detroit and Washington, D.C. are also being investigated.

The investigations come as activists from 18 different cities are in Washington, D.C. speaking against the common practice of shutting down low-performing or underenrolled inner-city schools. Chicago has been closing schools for various reasons for more than a decade.  

The investigations stem from complaints filed by the activists in each city, who charge that closings have hurt minority students disproportionately and in some cases are discriminatory.

“The fact is they pushed us to where we have to start a real movement,” said Jitu Brown, an organizer from the South Side of Chicago. Brown said the various groups from across the country plan to continue working together to fight back against school closings.

U.S. Secretary of Education Arne Duncan heard from the activists during a hearing Tuesday.