noun
school proprietor; school owner
Refers to the person who owns or runs a private school. Not a common term in modern Japanese; 学校経営者 or 理事長 are more typical.
その塾の校主は、地域の教育に熱心な人物だった。
The proprietor of that cram school was a person passionate about local education.
Compound of 校 (school) and 主 (master, owner). The exact historical derivation is uncertain, but the term likely originated in the context of private educational institutions.