They are supposed to have English to "Cambridge level Two" (I think that is the standard) but many buy the certificate or are poorly trained.
My partner is a teacher and she uses her own technique with these kids eg: it's not "what is the reference speed?" - to which you will get the answer : "sixty knots", it's "show me how you know you are travelling at Sixty knots"
.........and half the time they can't show her. (She isn't teaching aviation - just an example.