The DfE has published guidance for schools about setting up or reviewing complaints procedures. The guidance contains information on what governing bodies of maintained schools should do and sets out the legal duties with which they must comply. The guidance includes:
It’s aimed at governing bodies in all maintained schools and maintained nursery schools in England. It’s not intended for use by academies, free schools, further education or other post-16 institutions that are not attached to a maintained school, independent schools, and private nursery schools.
Also, see guidance on how to complain about a school.