I must preface my review by stating that I am fullheartedly aware that Bong Joon-ho's film, Parasite, is a very graphic, mature film that would most likely never be approved to be screened in my own high school classroom...With that being said, if in my dream world this movie were to be approved to be shown, I feel that it would be an extremely valuable experience for high school students in either an English or Social Studies course. Joon-ho's film works by way of strong symbology and metaphors (in fact, one character in the film even jokes consistently about their lives are "So metaphorical!"), which makes it a film extremely suited for an English teacher to demonstrate how figurative devices function. (The film uses houses themselves as central metaphors, illustrating how members of "lower" classes struggle to gain power in a world where it is nearly impossible to climb out of debt & poverty). The film is also clearly one with a strong focus on issues of classism and morality. It would be an incredibly worthwhile film to demonstrate what the "wealth divide" in a capitalist society practically looks like, and how South Korea's economic struggles are similar/different to our own.
I think a comparison of Bong's films with Jordan Peele's films would be very interesitng for their metaphors, but as you said, that would never be approved for a high school classroom.