Please note one exception to this rule. To take a sixth-level class in a subject, the student must have sat and have passed the end-of-fifth-level examination for that subject, and also must sit and pass the O-level or OWL examination for that subject. O-levels and OWLs for single subjects are given every Monday during the school year, and during the first Monday in July and August, provided the student gives the headmistress’s office two weeks’ advanced notice.