This thread:
https://www.ukhillwalking.com/forums/bouldering/teenage_boy_and_slopers__mantl...
got my goat a little.
Kids' bodies are still developing and very prone to damage that will produce long-term problems.
A chiropodist friend regularly bemoans the lasting damage parents do to their childrens' feet with ill-fitting shoes. Her view is that rock boots are an acute version of the problem. If a child climbs regularly and for long sessions (a few hours) then there is a high risk of lasting damage to the structure of the bones. As this is the first generation where large numbers of kids climb from an early age, we don't know the full impact; but the data from ballet etc. doesn't look good. Everyone knows bout the damage high heels do to childrens' feet; rock boots may be worse.
Similarly hands. Climbing places extraordinary forces on bones, tendons, pulleys, ligaments, cartilages. Yes, kids are light. And yes, the joints can withstand the loads. What's different is that it's not a short-term, one-off loading but a long-term, repetitive one.
People are starting younger and more intensively than ever before. But parents, please consider whether your vicarious pride is worth the damage that is likely to be accruing.