All schools must have a complaints procedure
Your complaints procedure must be published on your school's website so it's available to parents and the school community. You're required to have a procedure under section 29 of the Education Act 2002.
Your procedure should cover all types of complaint you might expect, including those against staff, the headteacher and governors, and serial complaints. Anyone can make a complaint about a school. They don't have to be a parent of a current pupil.
This is set out in the best practice complaints guidance for maintained schools published by the Department for Education (DfE), which you must 'have regard' to. This means you should follow it unless you have a good reason not to.
You must have a complaints procedure to handle complaints from parents and pupils. It must be in writing, be made available to parents, and set out clear timescales for the management