The story
From public + school: originally, “public” in the sense of "communal" and contrasted with personal tutors; later, "state-run" and contrasted with private schools.
Etymology from Wiktionary, CC BY-SA 4.0.
public school
Today it means: Certain private schools, particularly (initially) any grammar school operated apart from the personal lands of its students or (from the 19th century) the feepaying secondary schools which developed from or were modelled upon them; a British boarding school. Full definition →