A boy can hear his mom and her husband having sex in the next room.
Three implied sex scenes, no on-screen nudity.
John says, "Show us your jugs," to a girl.
A boy shows his penis to two girls (shot from the back).
John makes out with several girls.
When John meets Paul, he makes a joke referencing masturbation.
There is a scene were John exits a bathroom with a girl and it is implied they have just had sex.
There is a somewhat brief scene in which John sticks his hand up a girl's skirt and fingers her as she moans, then he drops his pants and she gets on her knees and the scene ends (it's implied that this is a daydream).
A great amount of the sexual references are implied.