It’s been “Rated R for horror violence and language, including sexual references.”
Now, just a warning to hardcore horror fans — it isn’t a “hard R.” The violence in it isn’t hugely bloody, in fact there’s less blood than in MAY. I was fairly sure it would be a PG-13, but I think what pushed it over the edge is some of the frank teenage dialogue.
Also, despite the girl’s school setting, there is no nudity. Just wanna make sure you don’t expect any.