Teachers have to figure out how to teach you whether you've got an IQ of 85 or 125. IQ scores don't matter; I've never once known a student's IQ and I have never thought "Gee, that would be helpful..."
For a teacher facing a class, and having a professional responsibility to teach each individual in that class, that might be true.
But there are plenty of other situations where honest acknowledgement of the gap might be helpful.