@cssftw
No paradox at all. Imagine a student who has topped the state in Eng Ext 2. But is unbearably shy: can't look you in the eye. Speaks annoyingly slowly. Or speaks with a stutter.
Conversely I have never done any NSW HSC English. Are you going to conclude I'm unable to communicate well?
By the same token say someone has great mathematical prowess. But cannot understand why mere mortals are so dumb. Hasn't got empathy to understand where the student (assume quite bright)'s difficulties lie. Has no patience. Couldn't be bothered to come down to the student's level. Would this maths genius make a good tutor for mere mortals?
Hmm... speaking is still a part of English, and regardless of whether you have a speaking disorder, you still will get marked down for not possessing adequate speaking skills. Moreover, Ext2 English doesn't really provide a clear picture of the individual's ability as an effective communicator, as all you are doing is composing a piece. Anywho the general trend is that [good in Standard/Advanced English] = [good communicator]. However it only gives an indication of that person's skill in communicating.
As you said, there can be circumstances where a person that is great at English, still could be a poor communicator. So while it is not 100% certain that this person will be a great tutor, I as a student, am comforted knowing that my tutor would most likely be a good communicator. Too many times have I gone to tutoring companies e.g. James Ann, where the teacher is incredibly smart in Mathematics, yet his foreign background caused him to have a fairly heavy Asian accent.
No I won't judge anyone if they haven't done HSC English, right now I'm desparate for an affordable tutor, however an 85+ English mark is still fairly comforting to me. Also, I don't often just find a tutor and then go straight to him/her, I often have a conversation with them, to determine their personality and their sanity. So finally, a good mark at English doesn't guarantee that the tutor would be an efficient communicator, however from my perspective, I would probably choose him/her over others. In the end, I suppose it's I that decides whether I keep this tutor or go for someone better.