mathanxiety - that's a fantastic article. It describes my dd pretty much entirely. We spent years basically assuming that it was just natural that writing lagged behind reading, especially given that she was an early fluent reader, and being told that the rest 'would come'.
I'm sure it does for some/many children, but not for all. A couple of points particularly stood out:
"a tendency to be extremely slow copying from the board, copying letter by letter, even when they can read the words" - I remember back in yr 2 we found that dd was being kept at copying two or three sentences all day that the other children had done in a morning session. Because she could read fluently, the assumption was that she was being obstinate and just refusing to do the work.
"realizing that it is your responsibility to teach spelling, and that these children do NOT learn simply by being exposed" again because dd could read, she never got any phonics instruction in English.
Eventually when she was in yr 4 and writing not improving at all (and she was being kept in pretty much every playtime to finish work which was still never getting done) we worked through a phonics programme at home, and also did 5 minutes per day handwriting practise & basic letter formation, which helped quite a lot.
I think that you need to keep on the case - I wish we had been much more aware of what was happening early on, basically dd only got help in the end because she has periodic meltdowns at school. The ed. psychologists assessments show her as being in the 99+ percentile for both verbal & non-verbal reasoning, which you undoubtedly wouldn't think was the case if you saw any of her written work from school.