This is actually my girlfriend’s memory. She recalls vividly accidentally seeing a horror film moment when she was a kid (most likely in the late 80s/ early 90s) where there are a group of teenagers terrorizing their male teacher and it seems to be after school because the lighting is magic hour or late afternoon and there seems to be an implication they are vampires but they don’t reveal it. I’m a pretty big movie nerd but I haven’t been able to figure it out. Does not seem to be Lost Boys or Village of the Damned. Seems vaguely familiar but I have no idea. I welcome guesses.