If he doesn't know that he's gifted (GT, HG, PG...) and he has noticed his differences, it may help to share that with him (with a caution against telling other kids--"it's a private thing"...). It may help him understand himself if you share it with him and discuss how it affects how he learns and understands the world around him...
*Horror Study Disclaimer*
On a personal note, I grew up not knowing that I was gifted or how gifted I was, and, when I compared myself to everyone else in my class and to my siblings and cousins, I concluded that I was stupid or that I was some sort of abomination (teachers had a hand in that one). I proceeded to try everything possible to make myself "normal," starting at around 10. No one told me about my giftedness (parents or counselors) until I had gone through drug treatment several times as a teenager. There was a lot of anger directed at those who had kept the information from me after I was told and had read about profound giftedness.
