Children's street culture refers to the cumulative culture created by young children. Collectively, this body of knowledge is passed down from one generation of urban children to the next, and can also be passed between different groups of children (e.g. in the form of crazes, but also in intergenerational mixing). It is most common in children between the ages of seven and twelve. It is strongest in urban working-class industrial districts where children are traditionally free to "play outside" in the streets for long periods without supervision.