Yep the age is 3-9 for the kids menu's. I however don't have a problem at most non-buffet's having my 14 year old (who doesn't eat much and likes the kids meals) order from the kids menu's.
Actually we have been reaffirmed from many of the disney resteraunts that anyone of anyage can order off of the kids menu. Even us adults and it's not breaking any of the rules.
However, if you are asking because you will be using the free dining or a dining package it might make a difference and they might be strict about the age limit.