I think it's the same issue that many people have with the "gifted" label itself. Ideally, all kids would have their unique educational needs met. Most of us are dealing with situations where that is not realistic. We need labels in order to have a way to talk about differences that are real. A linear progression (G, MG, HG, EG, PG) is a one-dimensional way of looking at something very complex--it's inherently limited. But it's becoming accepted educational parlance and it's better than nothing when we need a way to talk about our kids.
Maybe a good practice would be to qualify the labels to make them more precise-- my DD is verbally HG, but DS is borderline EG/PG and globally gifted. Both are gifted, but in very different ways and have different needs. I think if I describe them that way, you have some idea of their abilities and relative strengths and weaknesses.
The original question was about the relationship of IQ to the meaning of HG. I think it's clear from people's posts that we agree that HG means more than a certain IQ score, but that IQ scores can be used as a guideline or estimate of LOG.
