By junior year of high school, teacher and student alike could swear in heated class discussion. This was limited to the social studies department however, because they were the coolest teachers, minus the music directors. Everything but the f-bomb was in play, within reason.
EDIT: Okay maybe not, because "cunt" and "cocksucker" would've been flagrant fouls. But I got away with "hell," "damn," "crap," "shit," "asshole," "jackass," "dumbass," "bitching and whining," "pissing and moaning," and "pissed off." My psychology teacher used "dildo," "vibrator," and "dickhead."