I've only seen the first one (shameful admission) all the way through. I don't remember that specifically, but it very well could be from somewhere else including Cheech and Chong. I'll have to watch all of them now. But I definitely remember being in my gr. 10 Civics class (same classroom as home ec), and watching a girl named Jessica* insufflate cleaning powder - may have been Ajax, may not have been. Peer pressure; she had a reputation of being a "coke head", but I doubt anyone did enough coke in my HS to be truly labelled as such.
*names may or may not have been changed to protect the stupid.