I guess there are two ways of looking at this. A youngster who is not yet a real marksman may well pull off a good shot with a gun that they are not afraid of. So too are they more likely to love to practice with a shoulder friendly cartridge. For adults I favor a Minimum of 25 caliber. For kids I would favor which ever legal gun that they can shoot best. I have taken deer with the old 222 without loosing any. Even one with the 22 Hornet which is no longer legal in our state. I don't recommend the 22 centerfires at perfect deer calibers but for some young shooters I can see a place for it. That said it is the responsibility of the hunter and parent to insure a quick clean kill.