Dirt-Bikes - the offspring of the popular mountain bikes
As already mentioned, Dirts are not suitable for touring, but are designed exclusively for acrobatic maneuvers. There may be parents who are convinced that a dirt bike will bring joy to their offspring, but this is only true if the offspring shows a massive penchant for dirt biking, otherwise a dirt bike has no place under a child's bum - pure frustration would be pre-programmed!
The common size is 26 inches, furthermore a gear shift is usually not used. Completely slimmed down, only with a single-speed crank, dirt bikes keep you bound to their purpose.
Simple steel, often referred to as HiTen, is not recommended as it is not only heavy, but can also break. Rather, CrMo or CroMoly steel variants are recommended. These are harder and generally robust enough. Aluminium is only a limited alternative. Lighter but less stable, this metal can not mix sufficiently with the specific demands.