Right now I have xl185s and its perfect. Anywhere from a 125cc to a 200cc depending how tall and experience the teenager has Answer Since you're asking this question, I assume he is just starting. Depending on the size and weight i'd go with either 125 four stroke or 250 four stroke.
If he really wants that brute force, go with 125 two stroke, but I bet it will be quite scary at first Also, where will he be riding? If he wants to go on the road as well as off-road, then a dual sport is your best choice (don't mistake it with an Enduro. Enduros are often mistaked with dual sports, but they are much more expensive and designed for professional racing mainly).
If your kid is only interested in dirt riding then a motocross bike is the best bet.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.