The Secrets of Drearcliff Grange School — Kim Newman

A week after Mother found her sleeping on the ceiling, Amy Thomsett is delivered to her new school, Drearcliff Grange in Somerset. Although it looks like a regular boarding school, Amy learns that Drearcliff girls are special, the daughters of criminal masterminds, outlaw scientists and master magicians. Several of the pupils also have special gifts like Amy's, and when one of the girls in her dormitory is abducted by a mysterious group in black hoods, Amy forms a secret, superpowered society called the Moth Club to rescue their friend. They soon discover that the Hooded Conspiracy runs through the School, and it's up to the Moth Club to get to the heart of it.