どれくらいの年齢の人を教えているの？って英語でなんて言うの？

「どれくらいの年齢」＝ what is the age / what age / what is the age range / how old

「どれくらいの年齢の人を教えているの？」＝　What is the age of the people you teach?　 / What age are your students? / What is the age range of the students you teach? / How old are your students?