Boy in the water - Stephen Dobyns

Lying deep in the wooded New Hampshire countryside, Bishop's Hill Academy is a school running out of control. Jim Hawthorne, newly appointed head, is eager to escape the demons of his own past and determined to succeed despite the shadiness and resentment amongst his staff. However, he is unable to stop a terrifying madness being unleashed when a boy is found dead in the school swimming pool.
Serene on the surface, the school's ivy-clad campus masks a long history of corruption and violence, and as winter closes in, the routine of classes and meetings gives way to savagery and murder.