This student reminds me of one of mine. She's also in eighth grade, has taken lessons since first grade, and improves VERY slowly. She is very uncoordinated in all areas -- softball, flute, walking across rooms (she trips over the bench so much that I move it before she comes in.) She loves the piano but it is very difficult for her. Thankfully there is so much intermediate repetoire out there that I am able to keep her interested without advancing her too fast. If I give her a piece that is too challenging she starts to go ballistic. I try to give her music that will impress her friends and sneak in some "good stuff" along the way. I give her some "cool" sight-reading stuff every week, usually three levels below where she's at. I have seen more improvement lately, so if you can just keep your student going for a while longer, she might "turn the corner." Good luck!