Best way of explaining is using the gold analogy.
But I think explaining it to a person in his/her early teens will be quite diffiicult. Best to wait till the person reaches late teens and then explain
Yes, I agree from what you have said. We should wait the right time when we should introduce bitcoin to someone. Most of the teenagers or children are not yet that business minded or have a mindset to earn money, because in that age, children or teens just want to enjoy their life, easy go lucky something like that. Like what you have said, the right time to introduce bitcoin to them is in their late teens because they are matured enough in late teens age.