I have seen someone take a hit in class. Its plausible. It was just a tiny hit from a sneakatoke, and he held it in til there was no smoke, but still. Any other teacher would have smelled it and made the CPO's come and search everyone, but this teacher was utterly retarded. The highschool was short on English teachers and was obviously desparate, I mean she was not fit to be teaching first graders, so needless to say, sophomores ate her alive. I used to ask to go the bathroom at the beginning of class, and not come back and she wouldnt even notice. Or just walk out when she was at the board writing. ANd no one did anything in that class but talk and screw around, but everyone had A's and B's. I also had a friend say he took a rip during woodshop, which is definitely plausible just because of the fact it was a pretty big shop and it had a bunch of ventilation.
But to actually blow smoke out in front of a teacher and have her not do anything about it seems pretty implausible. Even my retarded 10th grade English teacher would have called the campus police at that point. I dont know though, stranger things have happened. Like dannyking said, I'm sure people here could tell you some pretty crazy true stories.
Back to the topic though, I definitely know a few compulsive liars. I have a friend that lies about the most retarded shit. And not little lies either, he'll make up whole stories that are completely bullshit. Or another thing he likes to do is steal stories from other people and put himself in their place. Its like stoney said, he just wants to impress people...but hes retarded so he needs to lie to do so.