All the monsters of high school — mean girls, hormone-addled boys, transphobic administrators, predatory biology teachers — are represented in K-12, an ambitious feature-length music video written and directed by singer-songwriter Melanie Martinez. With comic vignettes and almost ritualistic dance sequences set at a “sleepaway school,” the cynical, magic-realist tone is part Harry Potter and part Heathers. The film was edited by Emilie Aubry and Niles Howard; Josh McKie was the cinematographer.