The school has to be out in the boonies for protection. You don't want drunken Salemites just crashing into the walls. Or the odd bizarre guy with a gun. They have to actually WANT to hit the school in that location. And with the number of kids we see, it's most likely a K-12 school, with most kids going to the local parish school that Hope and Aiden set up, and danced in the hallway.