just like you explain money to them. maybe a bit later since bitcoin is a bit more complex and it would be good if they have an understanding what money is.
This is going to be a good way to explain what bitcoin is to the teenagers. Because while they are young it is good if they are going to get exposed in the bitcoin way of earning. And for sure that is going to help them more as they grow up and that is going to help their educational fees to cover up their expenses and their parents too.