I don't know Quantum - can he just use typing instead at school?
It makes me think twice just a bit - if his handwriting is laborious enough that he's dictating during group projects, it sounds like it's quite a bit slower than his peers. Have you tried measuring his speed at home just to see if it's significantly slower than expected for his grade/age level?
If it is, I'm a bit skeptical that handwriting practice at his age is going to speed it up.
I'm also not 100% convinced I'd rely on a teacher's assessment of handwriting ability or sometimes even an OT's assessment re dysgraphia diagnosis. My extremely dysgraphic ds has an OT assessment that falls within average - all that really says is that he's not motor-disabled to the point he can't do the task, it doesn't address what's going on neurologically that actually results in his dysgraphia. I realize I'm not explaining this very well at all.... I'm in a hurry lol!
Has your ds had a neuropsych eval ever? Was there a gap in processing speed vs other subtests such as verbal etc?
Best wishes,
polarbear
