Madame Macavity's Witchcraft Academy is the preeminent educational establishment for the discerning young witch or wizard. All students are instructed in the essential skills of witchcraft, as well as manners, deportment, and behaviour befitting a member of the upper classes. Safety standards are the highest of any boarding school in the country, magical or otherwise; accidents are almost unheard of, and both teachers and students may experiment with their magical abilities in safety and comfort.
So it's somewhat embarrassing, to say the least, that the entire staff and student body appear to have lost their memories.
It's up to the assorted teachers and students of Madame Macavity's to sort out who they are, what's going on, and what exactly they're going to do about it.