I rather to have some rule that are flexible, rather to be up to company commanders to decide. Thats how it works, generally Battalion staff would have general rule about 16 and above being able to fire. But anything Battalion does not say, Companies are welcome to change. 10th Illinois do allow 16 years old and older to fire but do not allow under 18 to camp without consent or alone.
However, battalion was able to change the rules for one event when the Boys Scouts (American Hitlerjugend) (mostly 12-16) to join 31st Wisconsin to fall in for the weekend, march, drills, in uniform, even fight in battle with their own rifle, no medic stuff. There was 20 of them in fact. Was very interesting but knowing Boys Scout, they have capablity of discpline and the organizgation itself is well repuated, i would bend the rules for them. Which my battalion did and it was a success, all the boys had a great weekend of their life.