Unman, Wittering and Zigo (1971) review

John Ebony (David Hemmings), who's married to Silvia (Carolyn Seymour), accepts a position at the all-boys Chantry School because the previous instructor supposedly fell off a cliff and then gets rattled when his students claim that they committed the "perfect crime" and killed his predecessor - panicked, he tries to report it to the headmaster and a colleague in the art department, although they brush him off.  I can't speak for everyone else in the field of education, but I've had the great misfortune of being a substitute in a class where it felt like most of the kids in the room were actively conspiring to get me - since I didn't know who any of them were they'd figured out a way to "swap names" and confuse me further - and this does a superb job at creating a real sense of dread in an educational setting (the way the snickering deviants say "sir" repeatedly is truly menacing).  It has its missteps - after receiving the wallet I'd have immediately gone to the police and the attempted sexual assault at the end is an ugly moment - but it's still a chilling depiction of youth-gone-wrong (perhaps due to an absence of age-appropriate females?).