Counterpoint: I have been programming since I was 6. I skipped a grade and school and was still in more advanced maths courses than anyone in my grade, though not as much as you seem to have been.

The only bit of this I usually ever mention: the bit where I've been programming since I was 6. And I don't say that as a form of bragging or a form of indicating my skill; it is merely the first sentence in response to the question "how did you get into programming?"

The main reason for this, though, is that I'm embarrassed by the fact. I feel like, if I've been programming for so long I should be better at it than I am. There seems to be an expectation that just because I taught myself how to program using little more than the source to BASIC games that I should be a super-rockstar or something and I'm not.

Point is, I don't mention it because the fact I've been programming so long doesn't really mean shit.

[EDIT: I also know a number of people who never touched code until college and got really damn good before they graduated, let alone after that.]