What does O.W.L. stand for in J.K. Rowling’s Harry Potter books?

In J.K. Rowling’s Harry Potter books, O.W.L. stands for Ordinary Wizarding Level.

O.W.L.s are subject examinations taken by Hogwarts students during their fifth year. The results help determine which advanced subjects students may continue studying in their sixth and seventh years. Harry, Ron, and Hermione sit their exams in Harry Potter and the Order of the Phoenix.

The abbreviation is a wizarding-world version of the familiar school examination acronym O-level, historically used in the United Kingdom and other education systems. O.W.L. results are graded from Outstanding down to Troll, with several intermediate grades. They are different from N.E.W.T.s, the more advanced examinations taken later in a student’s Hogwarts education.