DS (almost 9) has what appears to be obvious dysgraphia but does not have a diagnosis. Most of his writing is very difficult to read, and looks like preschool or kindergarten writing. We were able to get him a IEP in first grade by using the diagnosis "developmental coordination disorder" and qualifying him as physically impaired. We had an outside neuropsych diagnose him with DCD. He probably could have diagnosed him with dysgraphia, but didn't give him an achievement test. He diagnosed him with DCD based on a fine motor skills test and other outside evals that we had (for instance OT and PT).
Without the DCD diagnosis, I am not sure that he would have qualified for services, and here is why. The school gave him the Woodcock Johnson Achievement test and his written expression composite was something like the 80th percentile. The school is looking for below average scores (probaby below the 25th percentile) on achievement tests. But tests like the WJ are so intertwined with cognitive ability that a gifted student would most likely not score in the below average range. If they do really well on one or two subtests, that will boost up their overall composite score. DS does awesome with spelling, his ability to write sentences in first grade was probably advanced for his age because he was reading way above-level, etc. So we really needed to go the poor motor skills route in order to secure services.
We also had issues with my DD and getting her services for writing. She scored in the average range for written expression on the WJ-Ach and even the WIAT (although it was scored incorrectly, the overall score was still average). Yet, she wasn't ever writing more than 2-4 sentences in class. Her motor skills and handwriting were good, but she had poor fluency and had no idea what to write. With her, we needed to go the Other Health Disability route and get her classified through her ADHD.
Some schools are not so "backwards". They will see that the student has large gaps in abilities and qualify them for services based on discrepancies. But that was not our experience.
FWIW, DS had made little progress with handwriting with the IEP in place. I think it's good he is getting more 1-1 attention so he doesn't space out in class, and the OT is teaching him to type. But it hasn't been a magic bullet
