What is eating at me right now is that we have worked so hard over the years to get her some help in the areas that she has clearly had difficulty in (mostly to do with executive function, attention, but she also has a documented expressive language disorder but not by the school). I feel like we've neglected the other part of her and have failed her in doing so.
This is always going to be an issue - there are only so many hours in a day. There is only so much time and money for any family to invest in any one family member. What is fair? What is reasonable?
St pauli girl's suggest to start with the teacher is a good one! It's possible that your daughter has learned quite a bit, but can't show what she knows due to the 2 E issues.
Has the school done IQ and achievement testing? What actual other diagnosises have been found? Do they seem 'right' to you? Keep posting here and we'll do the best we can, but the most efficient way to proceed is to hire a psychologist that specializes in psychoeducational evaluation. Look for one who
a) is familiar with Gifted Kids
b) is familiar with 2E kids
c) is willing to guide you how to best develop your DD's strengths, including talking to the school if necessary.
Good Luck! Remember that the hard work you have done must have worked pretty well for you to have enough slack to be worried about what you haven't done, right? Those gains are real and important. Now it's time to take the next step!
Grinity