The Ghana Education Service, which delivers pre-tertiary education on behalf of the Ministry of Education.
It employs and posts public school teachers, registers schools - private ones included - and runs the district and regional education offices that sit between a school and the ministry.
For a parent it is the escalation point above a headteacher, and the body a private school must be registered with. Asking a school to show you its GES registration is a normal question and a revealing one.