Student or Learner
The Cambridge International Dictionary of Idioms says that "a feather in somebody's cap" is old-fashioned. Is it true that the phrase is no longer used?
Cambridge Dictionaries Online - Cambridge University Press
You will hear it over here :
She gained all her starred grades, and is a real feather in her school's cap.
You will hear it in the UK, but I agree with Cambridge that it is somewhat old-fashioned.