While not everyone on the spectrum are either high or low-functioning (most are a bit of both, or neither, or "moderate"), there still are some spectrumers who are low-functioning and others who are high-functioning.
For example, this kid I used to know had what we called "severe autism". He was completely non-verbal even at age 9, had very obvious repetitive behaviours, couldn't make eye contact, had meltdowns frequently that were triggered by change or loud noises or the sight of other children, and spent every day in his 'sensory room', in diapers, and constantly had to wear a padded helmet because he sometimes hit his head with his hands as a form of stimming. The last I heard, he is in a care home for adults with learning disabilities that are unable to look after themselves.
That is the perfect example of a low-functioning autistic person. I'm not saying all low-functioning autistic people are the same as him, but he still ranks as low-functioning on the autism spectrum.
As a high-functioning Aspie, I feel like I'm both NT and autistic. The way I see it (and I'm not speaking for anyone else here), NT is red and autism is yellow, mix them both together and you get orange. I feel like orange.
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Female