Informal is best way
The Department for Education and Skills suggests concerns should be resolved informally. Apologies and assurances usually do the trick.
If the issue cannot be resolved , complaints should be put in writing. A three-stage procedure is likely: complaints to a staff member, the head, and the governing body. Parents can also complain to the local education authority or courts. The policy must be published and reviewed.
An independent school's handling of complaints must meet the standard laid down by the chief inspector. Two mothers who objected to religious education at a primary school found it took three years to go through all its stages.
Independent School Standards (England) Regulations 2003: DfES Guidance, School Complaints Procedure 2003 www.teachernet.gov.uk leamailingR v Secretary of State for Education ex parte R and D 1994