I agree having a professional's input goes a long way. We sought out a child psychologist after our DD was exhibiting some asynchronous issues. We both went to the first few meetings with the psychologist. Those few meetings helped my husband begin to understand our DD and where she was at. I had been worried that her current school wasn't meeting her needs. DH constantly disregarded my concerns. The psychologist said "a traditional school may not be what your daughter needs. Have you thought of project based or IB schools?" I nearly hugged her! Fast forward a few months. He is finally on board with open enrolling to a different district and, or moving! HUGE strides!
DH was in the talented and gifted program as a child, I was not. While much has changed in the 35 years since my husband was in first grade, his perceptions of school and how things work there have not changed. He still has lots of learning to do:-) All I can do is educate myself and when something is really interesting, I'll mention it to him. He's got to do this on his own timeline. The more he sees where she is at compared to other kids her age, the better.
I just wish he weren't so slow to adapt:-)

Grinity- what is 2SD & 3SD? I'm still relatively new:-)