I'm right behind you, if you think his english needs improvement, tell him. The regs require you to speak english for a reason.
There are a lot of foreign students at my airport, and some of them can barely speak and understand even less. It can become a huge safety hazard. One of them cut off a Lear 45 on short final one day, the Lear had been making plenty of radio calls, but student just plain couldn't understand. Another one yesterday was doing a first solo (I think), kudos to him for the accomplishment, but his instructor had to speak the students native language over the radio so he would understand another pilot's question (granted that is what it looked like from my perspective, it could have been different, but the timing was damn strange if that wasn't the case).
I've also heard of foreign students using translators on checkrides. Excuse me, but that's BS. If I were a DE, the translator goes, or you fail right now.
I know it's hard for them to live in a different country away from friends with a different language. It's great that they're putting the effort into it, but seriously, there has to be a line drawn somewhere. They have got to speak and understand english.