Find the correct procedure
Ask the school for its complaints procedure and check who receives the complaint at each stage. Admissions, exclusions, safeguarding and SEND decisions may have separate routes and should not be forced into a general complaint.
Write a focused complaint
State what happened, when, who was involved, the supporting records and the action you seek. Keep your account factual and save every response.
Escalate appropriately
Follow the remaining stages in the school's published procedure. If the process has been completed and you believe it was not handled properly, check the relevant route to the Department for Education or another body for that issue.