What actually is Legal Age?

We see a lot of violence these days and it is just most unlikely and devastating how many children bring guns to school. We all know that they didn't expect that one gunshot can take lives but just like me, have you been wondering what age is actually legal age to held children liable fro their actions? Somewhere I think that this roots at home when we don't let our children take responsibility for things he do just because he is a child. I think we should stop doing that and make them liable for everything they do so they will realize at an early age the concept of right and wrong. Sometimes I think it is just unfair to make parents liable for things that their children have done. Why does parents have to take the blame even if they have exercised due diligence? I just don't think this is fair. What I know is we're raising a pack of brat kids by cradling them at home and telling them that everything is going to be alright. I really think we should stop doing that if we want a better society in the future.