We only have done Explore test and are waiting for the report. For me I see this as a tool when talking to school as well as him. He is waiting for the results as he wants to see a proof that he knows more then he �should know�.
Of coures his social needs are important, but it may well be that he wouldn't mind being the youngest and smallest if he actually did make friends with his classmates, and they could 'get his jokes.' Yes his will lose out physically with older classmates, but it's easier to join an 'agemate' afterschool sport than it is to recreate a whole curriculum at school.
I think that it's fine to wait for the Explore results, or to have one year be fun and the next year provide challenge. But if you are feeling that bad feeling in your gut, then sooner or later you will have to adress the school issue.
Love and More Love,
Grinity