But surely you're not saying that if they haven't been taught to read from the beginning that there's no hope they'll ever master it?

No. I'm not saying that.

However, since you brought it up, I think the longer people play by ear, alone, and the better they get at it, the more they tend to rely on it.

Really, it can go either way. The other extreme would be the people who read incredibly well but are unable to play anything that is not written down.

Chris as a teacher, would you think it would be appropriate to discuss matters with the teacher. There could be tension, but sometimes as a transfer student teachers would 'probe' my brain to get an understanding of how I have been taught. From seeing 10 different teachers during my learning course as a student, I would say that all teachers have their own unique way of teaching. Its not all the same. There are many different methods out there - Suzuki, Dalcroze, Kodaly, Orff and more that enforce different skills and approaches to learning.

Its just a thought, ... would you ever talk to a collegue? (when you are teaching one of his/her ex students?)