They're not bad books- they're written with a good pace and a genuine concern to keep the reader guessing. My problem with them is their familiarity- it's basically the English public-school genre (Jennings etc) with the magical bits thrown into the mix.
If you want books about a wizard school, try The Earthsea Chronicles by Ursula Le Guin. Far superior stuff IMO, genuinely strange stuff as magic stories should be- a real sense of the mystical, the dark and the forbidden.
The HP books are the Big Mac of literature- easy to digest, undemanding but comforting, you know what you're getting.