Sleepaway Camp III: Teenage Wasteland (1989)

Psychotic Angela is itching to do what she does best: slaughter dozens of teenage campers. As luck would have it, the previous site of her murders has been renamed and converted into an experimental summer camp meant to bring together privileged and lower-class teens. On the day the youths are boarding the buses to camp, Angela runs over a potential camper with a garbage truck and assumes her identity. Once she has infiltrated the camp, the real terror begins.

Source: TMDb