Sounds like the meeting was a bit contentious. I'll start with a possible school point of view-- the small group may be how he learns best. Does he need someone close by to help him keep on track? I do think that schools do not like it when parents "know best". Some do and I love those schools, but some school teams have a thought in their head about what a child with special needs looks like and if your kid isn't it, they look for reasons why you're wrong.
Second, not sure why the school says no writing disability. This is a time when an outside assessor may be helpful. The profile looks similar to my dysgraphic though the testing gurus will certainly have something more reliable to say on this. Mine had other tests also.
What about writing in school? Do they have work samples? How's the handwriting? How's the timed writing?
How I would approach it is that he may or may not meet their criteria for a disability in writing, but emotionally, he is learning to hate writing. He has a negative emotional response. What can we do to support him?
And I'd teach him to type pronto.
