Being a school of magic, many subjects at Hogwarts differ from the studies of a typical school. Some subjects, such as History of Magic, derive from non-wizard – or muggle – subjects, but many others, such as charms and apparition classes, are unique to the wizarding world. There are twelve named teachers (referred to as Professors), each specialising in a single subject. All professors are overseen by a school head and deputy head. Transfiguration, Defence Against the Dark Arts, Charms, Potions, Astronomy, History of Magic, and Herbology are compulsory subjects for the first five years, as well as flying lessons. At the end of their second year, students are required to add at least two optional subjects to their syllabus for the start of the third year. The five choices are Arithmancy, Muggle Studies, Divination, Study of Ancient Runes and Care of Magical Creatures. According to J.K. Rowling, "very specialised subjects such as alchemy are sometimes offered in the final two years, if there is sufficient demand."^[17]

At the end of their fifth year, students take the Ordinary Wizarding Level (O.W.L.) examinations for all subjects in which they are enrolled.^{[citation needed]} Each examination consists of a written knowledge test and, where applicable, a practical demonstration of skills before a panel of proctors from the Ministry of Magic. Students who achieve a high enough O.W.L. grade in a particular subject may take its advanced course for the final two years, in preparation for the Nastily Exhausting Wizarding Tests (N.E.W.T.) given at the end of the seventh year.