A woman mentions that she will lose her apartment unless she blows the superintendent.
In the version I watched (streaming), there are several brief discussions about sexual situations, mostly by the younger characters. There is no on screen sexual acts. There is no on screen nudity. The sexual behaviors are either hidden or edited during production or perhaps were edited out later for commercial reasons.
A young boy masturbates in a library to a picture of a nude female chest by rubbing his crotch on the edge of a wooden bookshelf. We see him reach down in his pants, take the ejaculate out in his hand, and smear it across some books on a shelf. We see the ejaculate dripping from the books. In a separate scene, he rubs some on someone's locker, but the actual act of masturbation is not shown.
A young boy lays out a bra and panties on a bed and rolls a condom on, out of curiousity, but it is not shown.
A boy kisses a girl and we see their tongues moving back and forth.
A man and his two kids discuss their mother's affairs with other men a few times.
A scene from "Blue Velvet" shows Isabella Rosselini nude from the waist up very briefly and in a non-sexual way. Her breasts are fully exposed.
A teenage boy (and the camera) stares at a young woman's behind in her jeans. Later, the same boy stares at a woman's groin while she's sitting cross-legged in shorts. He leans forward and kisses her knee.
A man and a woman are implied to have been having sex.
A teenage boy wonders often whether he should sleep with his girlfriend or other girls. He talks to other teenagers about this, they suggest both. He also talks to his father about it several times.
A teen's girlfriend, seen in her bra, gives him a hand job, but this is only seen from upper waist and above. Her cleavage is exposed quite clearly, however. The teenager receiving the hand job begins to breathe heavily, then we hear him grunting as he twitches, implying that he had climaxed. After he finishes, she is seen rubbing a towel on her bed sheet, obviously to clean up his ejaculate. He asks her about what she's done with another guy.
A teenager tells another teenager that a certain girl would "move her pussy muscles" in just the right way, so you can blow your load in a few seconds.
When a boy knocks on his Dad's door and opens it, he sees his father trying to get a young woman significantly younger than him to perform oral sex on him.