One of many issues with the framework of “high-functioning” vs. “low-functioning” autism is that autistic people typically show much greater variability in the upper and lower ranges of their cognitive skill test results than the general population, even within the same person’s scores.
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ASD is associated with an uneven or spiky cognitive profile. While everyone has some variation in their cognitive abilities, the variation tends to be within a particular band (i.e., clustered around the 70th and 80th percentiles) rather than widely dispersed. […] To give you an idea of how dramatically disparate the cognitive abilities of autistic individuals can be, I had a bunch of scores in the 98th and 99th percentiles, but I also had a cluster that included the 8th, 10th and 12th percentile. I am simultaneously off-the-charts extraordinary and bottom-of-the-barrel impaired. In yet other areas, I’m perfectly average.
⤷ I Think I Might Be Autistic, Cynthia Kim