This is a decision that every photographer has to make on his/her own, but for me it's always some kind of a balancing act. I always try to consult the wishes of my young "models", but in the end I'm the one who is responsible for what the photos look like and that the posing doesn't look inappropriate for the age of the "model".
Here are two examples from my last teen - shooting ...
in the end it's the mix that counts!
in the end it's the mix that counts!
photo @ 2009 by Nina Hüttmann