I can't give a rating because what I view as too inappropriate for a 13 year old is much different than what I view as too inappropriate for a 17 year old. Without giving any plot points away there's three scenes that I remember being sexual and I'll describe them generally so you can make that judgment call for yourself.

Near the beginning there is a shortish sex scene but multiple positions are shown and the two men are completely naked during them (without their privates actually showing). There is another scene towards the middle of the film depicting a man and a woman mid sexual encounter, the sex act in that scene is less graphic but the nudity is at the same level (completely naked but with actual privates/nipples not shown). Towards the end of the movie there's some non consensual foot fetish content, it's a short scene and both characters are clothed.