Just like all kids gifted kids have lots of different temperaments and personalities. Just because your kid doesn't seem to have what you think may be the typical gifted child behavior that certainly doesn't mean that he's not gifted...just as having a kid that does act out in class doesn't make him gifted.
I agree with kcab that it sounds like he has a teacher that's appreciated him. I have not had one of DSs teachers mention giftedness to me (he is PG) and as a result none of them have tried to do anything to accommodate him. We have had a very rough year last year but since I've pushed in getting him accelerated he's been a different kid.
If he's reading and doing math as such high levels there's a very good chance (I think) that he'll test gifted but if they're already moving him up for some subjects in school you might not need to test him. I had to test DS just to get them to do something different for him.
