There is a scene where Katherine Heigl (13), Eliza Dushku (12) and other girl in the bathroom rubbing creme on her nipples, you only see a side view of her breast, but it's covered with creme.
Oskar seen rear nude in a changing room at the beach. Then he stands up against a teenage girl. It is implied that he is kissing her genital area, or possibly performing oral sex on her.