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.
In BBC's TV miniseries Sherlock, John Watson, (boyfriend to Sherlock Holmes) is discussing his various talents which include physical and mental flexiblilty, parenthetically adding at the very end of a long list "I learned the clarinet at school."