Under government regulations, all schools need to have a complaints procedure.
Any complaint concerning work or relationships in the class should be discussed initially with the class teacher. If the matter is not resolved satisfactorily or relates to some other aspect of the life of the school, then the parents should contact the Headteacher. The next stage would be to involve the Chair of the Governors in writing, which will refer the matter to the Area Education Manager for investigation.
For further details, please see the Complaints Procedure.