Sounds exactly like one of my kids.
I found a little test I was able to give him a few years back. It involved copying some text (a paragraph or two?). I set a timer for a minute or two and then counted how many words or characters he wrote. Then I had his sibs take the test and compared. He wrote very slowly, even compared to his little sister. Aeh would know more about this test than I do.
This might help:
http://www.schools.utah.gov/CURR/langartelem/Core/Handwriting/Speed.aspxWe decided to keep him writing. No scribing, no typing. Write. During school vacations, his dad would give him little assignments to copy text. That kind of thing. He writes much more quickly and easily now. I don't know if the problem would have resolved on its own as he matured.
He's also super-creative, which can be a mild handicap when faced with doing certain types of schoolwork (eg when answering a question about a story and getting mentally sidetracked as different potential events or endings occur to you). Is your son highly imaginative?
In our case, time and improved executive function skills have helped a lot. YMMV!
