Typically, CBT attempts to train auties to behave more like NTs; that is, to
mask their autism. It is repressive. We still need to know how to communicate with NTs and mask/compromise in that process, but we need to be at peace with who we are, too.
For instance, I have been collecting GI Joes & Barbies (for drawing references) for the last 30 years. I am not ashamed of them, but I don't bring them up outside of autism, drawing & miniaturist* circles. My 21yo son (in college) maintains a collection of superhero Legos, too.
Many here didn't get diagnosed until middle age.
You may want to ease him into it. Emphasize how he thinks differently. That concept is known as "neuro-diversity." If he qualifies for "gifted" class, get him involved in that, too. (Neuro-diverse people are usually at more ease, socially, with other neuro-diverse people.)
A counselor or school counselor may have other ideas on how to break it to him in a positive way, but the sooner, the better.
*I am on many forums with other adult collectors.