The Faculty (1998)

To the students at Harrington High, the principal and her posse of teachers have always been a little odd, but lately they've been behaving positively alien. Controlled by otherworldly parasites, the faculty try to infect students one by one. Cheerleader Delilah (Jordana Brewster), football player Stan (Shawn Hatosy), drug dealer Zeke (Josh Hartnett) and new girl Marybeth (Laura Harris) team up with some of their other classmates to fight back against the invaders.