Do they walk around the streets with them as well?
Stop. The percentage of youths "walking around on the street" in the US is virtually non-existent. I don't mind discussing or debating this topic if you'd like, but don't use hyperbole and try to indicate that, just because someone snapped a photo of what is obviously a rare occurrence (hence the reason for the photo) this is an every day thing like it is in Somalia.
I am very much into firearms, have done a lot of training with them, lived in all sorts of firearm friendly states and I have never, ever, ever seen a youth walking around openly with a rifle. It is illegal for a youth to carry a rifle like that - unless that photo was taken on a range or some equivalent.