I wish I had a nickle for every suprised parent of a younger daughter. Girls, especially 'not first born' girls, can show themselves in very different ways.
You are describing a classic story of 'Enforced Underachievement' - keep her right where she is - the fact that she is happy socially is a good indication in this situation, that her IQ is 'real' and not an artifact of the test.
I do not think that you are expecting too much from her. Reversing Underachievement takes time. Your oldest son might lead you to think that Gifties don't need adult teaching or guidance. This isn't true for many, many gifted kids.
You are seeing improvement - stay the course!
My hat is off to your school system, BTW, they may be able to save her from a life of misunderstanding herself.
Smiles,
Grinity
