prefect

noun

1. An official of Ancient Rome who controlled or superintended a particular command, charge, department, etc.“the prefect of the aqueducts; the prefect of a camp, of a fleet, of the city guard, or of provisions; the pretorian prefect, who was commander of the troops guarding the emperor's person”
2. The head of a department in France.
3. The head of a prefecture in Japan.
4. A school pupil in a position of power over other pupils.