With a child of my own interested in running a marathon, I researched marathon training programs for youth in the US (there are some!), injury rates and how these compare to high school running programs.
Timothy Noakes worked in Kenya for decades with elite runners. While running is part of the culture, running success is not. There is a strong genetic component tied to the Kalenjin (sp.) people. Again, the issue here is not whether children should run - they should. The issue is whether they should train for long distances.
The issue of barefoot vs shoed running is well studied at this point and I'd refer anyone interested I the work to Benno Nigg's Human Performance Lab as a resource. Basically it matters much less than you might think. Minimal shoes/barefoot running works for a subset of the population and small frames and light body mass contribute. Barefoot runners will also move injury from knee to foot and ankle.