In this 1998 sci-fi horror film, the students of Herrington High School discover that their teachers are being taken over by parasitic aliens, forcing them to band together to save themselves and the world.

The 1998 sci-fi horror film you're thinking of, where students at Herrington High School discover their teachers are being replaced by parasitic aliens, is indeed The Faculty (Review). This movie perfectly matches the description of a group of students banding together to fight an extraterrestrial threat and save humanity. It captures the quintessential late-90s blend of teen angst and genre thrills, making it a memorable entry in the sci-fi horror canon.

Directed by Robert Rodriguez, known for his fast-paced and stylish filmmaking, The Faculty brought together a compelling script by Kevin Williamson, who was a prominent figure in the horror genre at the time, having written Scream (Review). The film cleverly combined elements of classic alien invasion stories, like Invasion of the Body Snatchers, with the popular teen horror tropes of the era. This mix created a unique atmosphere that was both suspenseful and darkly humorous, appealing to a wide audience.

The movie also boasted an impressive ensemble cast featuring many popular young actors of the time, including Elijah Wood, Josh Hartnett, Jordana Brewster, Clea DuVall, and Usher Raymond. Their performances, coupled with the film's practical and special effects, helped to ground the outlandish premise in a relatable high school setting. The Faculty has since garnered a cult following, appreciated for its clever writing, energetic direction, and its contribution to the resurgence of teen horror films in the late 1990s.