My guess (and I am just a parent, not an expert): Your son is definitely smart (as in above average). Gifted - not sure at all. It wouldn't be surprising that he is ahead of the class with an additional hour of individual instruction year-round (which I would expect to be much more focused than in a classroom setting). When I look at the elementary school guidelines - they are set very low, and there is a lot of repetition built in (addition from 1-10, 1-20, to 100 etc.).
My kid tested as gifted, and while we don't do nearly as much academic learning as you at home, I think what is amazing about him is that he understands concepts very quickly, with minimal "instruction" and repetition. I still don't know how to teach a kid how to read. Though he reads in three languages well above official grade level. And while he is not at the same level as some of the kids on this board, his math is still years ahead as well.
So my question back to you would be about how your son learns. And was there anything unusual about him in his first years? For instance, at his second b-day, my eldest did 60-100 piece puzzles essentially by himself (though he did want us to sit next to him).

Last edited by rac; 07/09/15 10:56 AM. Reason: typo