I agree with Ned. When kids are toddlers, the color in coloring books, wallpaper, newspapers anything. To teenagers a blank wall is something to color in, to get your name out, a canvas. Give them space and it will be street art for everyone to see.

I don't agree with gang graffiti, e.g "Cripz, Bloodz" or anything like that. That promotes theft, assault, serious crimes, drugs etc.

Give them a place to do it.