D15 has always been like that.  In school, she does pretty much what she needs to.  I think she would feel like she is showing off if she did too much... and she goes to a pretty academically oriented, private college prep school.  But she still wants to blend in as best she can.
THINK at Davidson was a great experience for her this last summer, she could accelerate as fast as she was capable of going.  She loved it.  Sort of like being out on the open road, I guess 

  I notice this fall that she is more ready to extend.  For example, she is planning to ask her science teacher to help her register for a science olympiad test, and plans to study on her own for it.  I don't think she would have done that last year.