Yes most civilians would make poor soliders but guess what? That works for anyone doing anything that requires training! A person off the street wouldn't make a good surgeon or lawyer or firefighter. These jobs require certain mindsets, certain skill sets and, yes, a great degree of training. Also not everyone is cut out to be x, y, z. Some peole would break down in army training because it would be too much for them. Other ones simply wouldn't be able to do it or wouldn't be able to handle combat.
Children do require 'basic training' in a sense. They come into this world clueless and have to be taught things because they know nothing.
When I have a kid, I'm not hitting my kid. Such a thing seems unthinkable to me. You can teach a child discipline without violence.