Originally, school was for the nobility and (fledgling) bourgeois, so they could run their spreadsheets, wage wars, and impress people with trivia, everyone else’s education came from family tradition, neighbours (farmers talking farming stuff), or an education in the trades. Want to study geometry? At some point, the best option was to become a mason. And they would swear you to secrecy.

Universal education is a brainchild of Martin Luther, he wanted everyone to be able to read so that all could read the Bible.