A bit from a 'child's' perspective...possibly! Or an ex-child with a similar problem.
I don't know your family, Lynette - or what might be the problem with your Ds, poor him and poor you! But I do have experience in a way, which might help...not sure but here goes.
I had terrible school phobia when I was about 11.
The issue with me was insecurity at home, we had moved house, Mum started a mature degree at college and so wasn't at home, for the first time ever. Plus my sister had left our school to go to secondary school. I felt completely alone, and very very scared. I even had to walk to and from school alone (a couple of miles) and remember literally counting my steps - thousands of steps. I was so lonely.
I had certain physical symptoms - or imagined I did - which made me afraid I wouldn't be able to cope at school - I was terrified I'd feel sick or faint, of course these things happen when you are anxious enough. So I refused to go to assembly, many days I'd argue for ages before leaving the house, or occasionally manage to convince Mum that I just couldn't face it.
Mainly it was about putting everyone out, I mean I felt bad because they were all depending on me to go to school so that their lives could go on as normal, but I just felt so frightened and so responsible, yet unable to do what was expected of me.
Nobody seemed to understand and that made it worse. I lost weight, couldn't eat from fear, had dreadful panic attacks. It's still a vivid memory and I was certainly conscious of the reality of my feelings...however irrational they were.
The thing I wished for the most in the world, was for Mum to stay at home with me, or teach me at home...she wouldn't, she wasn't very confident about negating the whole system and was afraid it was 'indulging' me and would make me worse. But I still felt like a little girl inside and somehow, I think I 'needed' something that I'd perhaps never had - both my parents were very young and had depressive issues themselves, so I wasn't very secure emotionally.
What happened in the end, well I never got to see an educational psychologist or anything (I'd have been happy to have anyone step in and 'mother' me a bit, to be honest)
but I was gradually persuaded to rely on a girl in my class as a kind of support-friend. She would sit with me in the quiet room during assembly. She never put any pressure on me - though my teacher did, that didn't help - and eventually I began to feel secure because I had this girl, I was no longer alone, and therefore it wouldn't matter if I was to feel sick and have to walk out of assembly - I went from assuming the worst, to looking at life more positively, as if these things weren't likely to happen after all, as if i could deal with anything. That girl did me a huge favour just by being my friend.
I went on to secondary school with a better handle on things. I still had trouble sometimes but I'd proven to myself that I could cope. And I was never dragged kicking and screaming into school, to reach that goal - it was a gentle approach that keyed everything down.
I suspect the child someone mentioned who went in early to help their teacher, was getting a lot of security from being alone with the teacher - feeling somehow less alone, less afraid.
I'm sorry this is such a long post but I always really feel for a child when I see they have trouble going to school - and want to help their parents understand what it 'might' be about.
Again, your family is probably very different from ours...hope you don't think I'm implying anything about your Ds's reasons, they could be anything.
Good luck and don't stress about it - he'll be fine, school or not. Just try to be patient