I think that kids should be allowed to write Hive posts from early age. I am not sure how young. Instead of spending time on facebook they could benefit from being active on Hive. If people would start earning and engaging from younger age perhaps they would feel stronger connection. Also for some kids few hundred HP would already feel like a lot so perhaps they would treat it like something precious.
It shouldn't even be about the earning - it should be able having the ability to write, create, and interact with humans.