To gain life experiences through hood or drug lifestyle. Doing thug shit.
i.e. When growing up on the streets, or going through those few rough years of drug abuse that teach you how to be a man. You become a well learnded individual.
The term "learned the clarinet at school" is most commonly used by persons as a way of conveying the fact that they have been known to give fantastic oral sex, particularly on male genitalia.
"I learned the clarinet at school." John said, sending a wink in the direction of his room-mate.