Is the problem really handwriting/motor skills or spelling and grammar? My DS4 reads above the 5th grade level but couldn't (or wouldn't) write a complete sentence when he started kindergarten this year. He was a terrible speller, didn't know how to use capital and lower case letters correctly, didn't space words or use punctuation correctly, etc. Realizing all of this, his teacher has decided to devote all of his daily reading instruction time to working on spelling and writing and dealing with the perfectionism that rears its head in the process. This means DS4 isn't getting much reading instruction in school at all, but he is definitely being challenged, his writing is improving by leaps and bounds, and in just a month he's become much more comfortable with making mistakes. So, for now, I'm comfortable with focusing on writing at the expense of reading.
