In any pre-industrial society kids worked and they worked young and they worked darned hard. Those Skyrim kids would not be out running the streets all day - if they were rich kids they would be being educated etc and if they were poor they would be helping with whatever jobs their parents had - farming, chopping wood, sweeping etc. They would be too tired to be mouthy.
My own Great Grandfather was working as a railway clerk at the age of 13 and that was only just over 100 years ago.
Well if i remember right, there was a girl which says something like "I help my mother to sell groceries at the marked, mostly it makes fun, but it is hard work" (sorry dunno the right spelling - have the german version) And then there is the son of the jarl "Oh look, another traverl who wannts to lick my fathers boots, well done...." So there are different kids, and not ALL are rude like these others. Also don't make these innuendoes to this mod. It is not even allowed to talk about it here and they should not be allowed to give it as legal download.