A primary school governing body has apologised to parents after a message appeared on Facebook, apparently posted by a teacher, which described locals as inbred.
Excerpts from an online exchange were printed out and hung on fencing outside Westcott primary school in Hull.
One said: "No wonder everyone is thick... inbreeding must damage brain development." Another referred to seeing pupils queuing in a discount store.
The online exchange, allegedly between teachers at the school, has now been taken down.
Hull City Council confirmed it is investigating the incident in conjunction with the school's governing body.
The council said it could not confirm or deny reports one teacher has already been suspended.
In a letter to parents, chair of governors Mary Wallace said: "As you may be aware, there has been publicity around remarks allegedly made by members of Westcott school staff on Facebook. I write on behalf of all the staff and members of the interim executive board (governing body) to express a sincere apology for any offence caused by these remarks.
"I would like to reassure you that the matter is being taken very seriously. I have asked the local authority to undertake the investigation on behalf of the board in the interest of impartiality. We will be investigating the matter thoroughly and appropriate action will be taken.
"Our priority, as always, is the care and protection of our children and the continuity of their learning. I can assure you that every effort is being made to ensure this will remain the case."
One parent, Emma Bywood, 30, told the Hull Daily Mail: "It should be thoroughly investigated. Nobody has admitted anything in the letter and it's an apology from someone who hasn't done anything. The chair of governors shouldn't be left to apologise for it."