I taught 3rd grade for awhile. I play a game with my students. I would tell them 2 truths and 1 lie. They had to go figure out which one was the lie. It forced them to examine what people tell them, to learn to research things on their own, and to promote critical thinking and problem solving.
I would suggest that around middle school and high school that you pursue an online, maybe partial ground high school experience. It gets your kid used to crowds, classes with other students, different teaching and learning styles, etc.
You could do the same by having him take part college courses and part homeschooled high school courses during his high school years.
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ADHD-diagnosed
Asperger's Syndrome-diagnosed