It's less possible for the <70/60 child.
I was on a gifted committee way back when with a man who shared that we (gifted families) could never "win" with this argument, and he's probably right. He has since passed away, and in his memory I pass along his thoughts. Our GT kids need accommodations and acknowledgement, but probably not by comparing them to the other extreme, which is a challenging life situation in its own regard.
I can see his point, in particular because the idea is subtle. "The slow pace of learning in kids with IQs who are below the first percentile is comparable to the fast pace learning in kids who are above the 99th percentile."
A problem is that slow cognition in some ways is much more obvious than fast cognition. A teacher of average or above average intelligence (say, an IQ of 115) can gauge how slowly a student with an IQ of say, 60 (well below the 1st percentile) is learning. Because this person moves slowly and requires extra help, it's easy to for the teacher to compare to her own experiences. She can also draw on what she observes with average and above average learners. These factors help her make a comparison between the very slow learner and the average learners.
The same isn't true of an extremely fast learner (say, an IQ of 140, which is well above the 99th percentile). A teacher with an IQ of 115 can't compare with her own experience, and it's unlikely that she'll have dealt with enough kids with very high IQs to gain knowledge from them. Sure, she can see that the child learns faster, but without an understanding of how quickly people with IQs of 140 learn, and HOW they learn, she lacks critical insight.
The slower learners also benefit from large group of specialists who understand the needs of slow learners. It's too bad that the same specialty just doesn't exist for the gifted learners.
Obviously, courses on the needs and abilities of gifted students would help a lot here. But I wonder how much even these courses, as currently designed, really help. My concern (without knowing a lot about them) is that they focus on lower percentiles (such as the 90th or 95th), and so don't really reflect giftedness or high giftedness.
Another little point: getting an accurate IQ score for kids with very low IQs (< 2 or 3SD) is just as problematic as it is for kids with very high IQs, and IQs can vary by 10 and 20 points from test to test.
Val