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
Everyone is really interested if we are talking about money so it only means that if you are going to teach children about bitcoins then it will not really productive to them because all they want is to play but there will be a chance for teenagers to be interested because some of them might want to get rich earlier as they can.