To answer this, we need to know the general area of where you live, and if your grandson can function in mainstream settings.
Our 13 year old son will be doing Boy Scout and tech / programming camps this summer. If they follow their interests, they will meet like minded kids, and being with like minded kids is more likely to lead to productive social interaction. And, well, when they follow their interests, they have a great time
I must warn you, however, tech / programming camp is very expensive. We're looking at it is an education investment. Part of our son's eventual professional training.
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).