I shoot all the time, this will be the first gun that I actually own.
I was given a similar 20 gauge shotgun at roughly around the same age and it worked out perfectly. If it were a 12 gauge I'd possibly reconsider, but a 20 gauge doesn't have nearly as much kick to it.
Heck my younger brother (who is around your age now) has a 20 guage pump action himself.
I think he is too young to be using a gun at that age.
Its a perfectly acceptable age. Hunter and gun safety training courses usually start around 12 years old in any case.