There are about 3 or 4 sex scenes, all between underage characters, mostly comprising of implied nudity although one sequence shows a female nipple briefly and some show extremely brief or obscured male and female rear nudity.
In some sequences, teen female characters change into or out of bras, but these sequences are pretty short and no nudity is shown.
In a handful of scenes in a single episodes, there is explicit discussion of STDs and birth control methods. At one point, instructional diagrams are shown featuring different styles of female pubic hair.
In a couple of episodes, it is heavily implied and speculated that a character was raped.