The Faculty (movie, 1998)

When some very creepy things start happening around school, the kids at Herrington High make a chilling discovery that confirms their worst suspicions: their teachers really are from another planet! As mind-controlling parasites rapidly begin spreading from the faculty to the students' bodies, it's ultimately up to the few who are left – an unlikely collection of loners, leaders, nerds and jocks – to save the world from alien domination.