Ghoul Studies Class

Ghoul Studies was once considered for being removed from the curriculum, but after loud and destructive protests by Hogwarts' resident ghosts, the class has remained. However, Ghoul Studies is only taught once a week during the semester, overshadowed by classes that are deemed to have more importance and relevancy to the living. It also stands only as an elective, and is not required

Ghoul Studies--aptly named--is the study of ghosts, poltergeists, and other beings that no longer qualify for the mortal realm of the living. The class consists of speculation over the afterlife, the physical limitations imposed on ghosts (what they can and can't do, can and can't touch), a brief history on famous people that are now ghosts, as well as the reason behind their continued existence.

In large part, the class is ground in speculation, though the students do have the help of resident ghosts to try and better understand their predicament. Still, considering how little can be proven in the subject, it's likely only a matter of time before it is finally removed from Hogwarts.