Defence Against the Dark Arts was a required subject from first year to fifth year.The curriculum of the class varied greatly depending on what the professor at the time deemed appropriate. Due to the jinx on the teaching post that was present before Lord Voldemort died, many teachers had been appointed to this post.

Tom Riddle twice applied for the Defence Against the Dark Arts position, the first time shortly after graduation from Hogwarts when he was turned down by Headmaster Armando Dippet, who claimed he was too young but invited him to re-apply a few years later.

"The Dark Arts, are many, varied, ever-changing, and eternal. Fighting them is like fighting a many-headed monster, which, each time a neck is severed, sprouts a head even fiercer and cleverer than before. You are fighting that which is unfixed, mutating, indestructible. Your defences must therefore be as flexible and inventive as the arts you seek to undo." — Professor Snape discussing Defence Against the Dark Arts during a sixth year lesson in 1996

Many years later, after becoming steeped in the Dark Arts and starting to use the title "Lord Voldemort", he visited the school and applied again, this time to Dumbledore. He was refused again. According to Albus Dumbledore, after the second refusal, no Defence Against the Dark Arts teacher held the post for more than one school year. Dumbledore believed that this was due to Voldemort placing a jinx on the position, a belief that was popularly spread throughout the school.

The lessons generally had a practical approach, with the cases of competent teachers believing that when it came to the Dark Arts a practical approach was the best way, with theoretical assignments given as homework. Inadequate teachers, such as Quirinus Quirrell and Dolores Umbridge, who were focused on theories alone, hampered the learning of defences as they would not be providing students any practical experiences

In the fifth year, Ordinary Wizarding Level examinations were taken; as such, students spent their time learning new topics and possibly revisiting the past four years of lessons (depending on the teacher). As part of their Defence Against the Dark Arts O.W.L., students had to sit a written exam one of the questions asks to describe the five signs of a werewolf and after students must complete a practical exam of; counter-jinxes, defensive spells, the Boggart-Banishing Spell, and the Patronus Charm (for bonus points).

To advance to the N.E.W.T. class, a student had to first achieve a high O.W.L. score of either "Outstanding" or "Exceeds Expectations"; most teachers set the bar at "Exceeds Expectations".