A cross between Sherlock Holmes and Hogwarts (but set in the real world).

Stevie is a modern-day Sherlock Holmes who gets accepted into a prestigious academy for gifted high schoolers. Her main objective in applying to the school is to solve the murders of a student and the Academy's founder's wife which happened in the 30s. After she arrives another mystery comes along and her attention is diverted, though it's very likely that everything is connected. It seems like the central crime of the story won't be wholly solved until the last instalment of the series. But I have nothing against that idea since it is a good mystery and the books aren't that long.