In Star Trek VI, Uhura attempts to speak Klingon without recourse to the Universal Translator because she is trying to impersonate a Klingon and fears that using the Universal Translator would "out" her as a non-Klingon. It seems that Uhura does speak some Klingon, but she is obviously not comfortably fluent and makes some mistakes (but apparently not enough to be outed).
Is there anything known, for any time period, as to how many or what languages a typical Starfleet officer knows or is expected to know? Is there a required language curriculum at the Academy (e.g. must take or pass competency exams in English, Klingon, and a third language of the student's choice)? Does basic childhood education on Federation worlds follow specific practices as to what languages to teach, so that the majority of Academy students arrive with a basic set of expected language skills? Does it scale with rank (e.g. being promoted to Commander requires achieving a B1 in either Romulan, Cardassian, Ferengi, or the national language of a Federation homeworld other than the candidate's home)?