The Devil's Playground (1976) 
Perhaps the strangest film I've come across thus far in my trudge through unexplored Nightmare USA territory, in as much as it is neither horror nor exploitation as such, but more an in depth drama surrounding the young boys of a Catholic seminary and the priests (or 'brothers') who teach there.
Still as relevant today in many ways as it was when it was made almost 40 years ago, the themes of sexual exploration vs. repression and the religious connotations linked therein certainly provide the viewer with some food for thought.