When I was in 6th grade, I went to a boy's school in New York City that had a 22 rifle range in the basement. How things have changed. I bet you won't find a lot of those in midtown Manhatan anymore! In any case, I discovered this was a sport a not-overly-large kid could compete in on an even basis (prone shooting only). As an additional benefit, the range was indoors, warm and dry. No need to go out and have some giant second-former pound you into the mud. That started a life-long love of firearms. The next step was competitive pistol and rifle in college and, joy of joys, shotgun shooting and my first pheasant. After that, it came fast and furious, birds, big game, dangerous game, anything that would go bang, anything you could eat.
I started my older son shooting at 9 and he has developed into a fast, natural shot, both on clays and birds plus being not bad with pistol or rifle. He has his first double, a 20 bore SKB O/U, and has been promised the gun my father gave me as my graduation present when he graduates college, with his initials added to the stock oval. The younger boy (10) has shot rimfire rifle and seems to be developing into a fair shot. I have every hope they'll divide up dad's collection rather than let it go to the auction houses. The thought that, a hundred years hence, someone may refer to a gun as his/her great-grandfather's is not a bad form of immortality. To encourage this, the rule about adding your initials will be ordained as family law.