This film was featured as an episode of Mystery Science Theater 3000, but it's actually not that bad. It's a rather famous B-movie, and "I Was a Teenage..." became a kind of catch-phrase (I Was a Teenage Hairdresser, I Was a Teenage Stunt Man, I Was a Teenage Teenager... you get the idea). It's a rather well-made film, despite the B-movie acting, a fairly absurd premise, and some entended sequences of general goofiness.
The plot centers around a - wait for it - teenager, named Tony (played by a younger Michael Landon than you probably remember). He gets into a lot of fights - and apparently has a bizarre penchant for milk-throwing - and is constantly in and out of trouble at school. He has a girlfriend (played by Yvonne Lime, who was dating Elvis at the time of filming) who sticks by him, despite his random bouts of rage. Tony's father is perhaps the most dejected dad ever seen on film. When Tony gets into trouble one time too many, he is sent to a psychiatrist, Dr. Brandon (Whit Bissell, who I like much better in The Magnificent Seven). Dr. Brandon, a very experimental shrink indeed, injects Tony with a sedative and hypnotizes him into becoming a werewolf. It's a regression thing that I don't quite get. Anyway, wackiness ensues, and soon his classmates start dying.
I like this movie for the campiness and the way it takes Tony's wolfiness and misanthropy a little more seriously than it should. It's not particularly scary, except perhaps for a musical number performed by an elfen blonde guy, and that's really just scary because of his pants. :P