My daughter is similar to that. She was dx last March with ADHD. She is very bright, she gets what is being taught and doesn't want to linger on it. Unfortunately, her lack of doing her work in a timely manner is showing on her grades. She is in 3rd grade now. She started kindergarted reading at an end of year level, stayed way above the reading level through 1st grade. By the start of 2nd grade the rest of the kids were catching up, by the end of 2nd they had passed her. She doesn't like to read, she has the thought that since she knows how to do it, why bother doing it anymore.
I have also been told, by her first T, that she is emotionally delayed. She has the emotional reactions of a toddler. She is learning to deal with her emotions, but still has a long way to go before she is at her age level emotionally. I initially decided to not medicate her. I wanted her to learn coping strategies first. Since her grades have started slipping, I have decided to try meds to see if her grades will turn around.