I agree about the writing PolterGoose but when the basics of the skill is there but there is evidence that the individual is becoming anxious to the point of illness when would it be time to try an alternative? My DH had similar struggles at school as our DS. He was punished relentlessly due to it and told pretty much the same as my DS is being told, now you would be luckily to get him to sign his name on something, so all the focus on handwriting in school was pointless really.
OK peanutbuttercup here are some ideas which we used as parents and some which have been used at school for DS, not sure if it will help your Ds or not.
HOME (over the past 2 years)
a) story frames- starting with 3 sections (a bit like what cartoon makers use to begin with) beginning, middle, end - adding more sections as he gets used to doing it. We worked backwards so DS new the ending first then he just had to fill in the blanks.
b) Mind maps, spider graphs
c) Work on the fine motor skills every DC's develop differently, bendaroos were ideal for this.
d) Dictaphone, then DS replayed himself and wrote it down. This didn't work too well, my DS can tell you a wonderful, lengthy story but as mentioned above takes a long time to write it down.
e) Brain storm the basics eg characters/setting/plot etc, jotting down key words then DS uses this to complete a story.
most successful was the story frames, but saying that he tended to focus more on the pictures he did. 
SCHOOL
a) breaking up the work into smaller sections (green, amber, red), similar to story frame but without a picture to help. This could be done on an A4 piece of paper or a whiteboard.
b) small group work so more help from the teacher.
?????