NAPERVILLE, Ill. (AP) — A suburban Chicago high school says it has disciplined a group of students for a racially insensitive ad posted on Craigslist.

Naperville Central High School Principal Bill Wiebrook sent an email to parents Monday saying administrators became “aware of a racially insensitive electronic post and worked as quickly as possible to investigate and address this with the students involved.”

The ad showed a photo of an African American student under the words “Slave for sale (Naperville).”

Details of the discipline weren’t disclosed.

The ad follows an Oct. 26 incident at a Buffalo Wild Wings restaurant in Naperville in which some customers said they were asked by restaurant employees to change tables because a regular customer nearby didn’t want to sit next to black people. The restaurant fired two employees involved.