bjatoa, it is going to take a while for your son to process the information. I admit I was a little more circumspect in what I told my son, but he was also younger. Regardless, every child has their own way of processing new information, and you are likely to get questions or indications of emotions at odd times over the next year. Much of he deals with it will depend on how he saw himself before he got the term.
To the OP, I am firmly in the "tell them," camp, but obviously it should be done in an age appropriate way. How much any of us go into details depends on what you sense from your child, how much they seem ready for and interested in. For many kids, is it enough to be told their brain works differently, that difference has a name called AS, it comes with gifts and burdens, and now that teachers know they will be helping out with the burdens.
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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).