Thanks for your replies zoo and leap and some really valid points.
We haven't had him assessed for anything underlying, I've discussed with some of the professionals involved in his care and there's nothing that seems to indicate this but I'd be happy to have an assessment to be sure, from what I know though that's not easy to get unless the school has concerns? What's an EHCNA?
I think it's a combination of can't and won't, art/play therapy has been attempted, he doesn't like that either. The only person who can sometimes get through to him is the school nurse, she's due to see him again next week. He's happy when he's not at school, when we tried a reduced timetable back at the beginning he just got stuck and didn't move forward for a long time. I think if he had the choice now he would just go into school to sit in the send room for an hour and not take any steps to progress, he's firmly in the avoid frame of mind currently. Like you say zoo if I allow him to stay home I can see his world rapidly shrinking, he gains confidence and is happier when he's with his friends.
He understands the mechanics of anxiety, he's been to an anxiety group (wouldn't participate) had loads of explanations/techniques but again doesn't acknowledge any of them.
Transition wise yes school gave him his own personal tour, we had meetings before, his therapist tried to prepare him and the school nurse did some work with him too. He's been assessed by child wellbeing team over the summer, they discharged him as he's getting into school (albeit not getting into any classes)! he doesn't meet the threshold for CAMHS apparently and he told the therapist he doesn't want any help.
He goes into the office in the morning, a member of the send team meets him and takes him into their room, they've tried to encourage him to stand outside some of his classes with a send teacher to listen in and get used to the environment, they've taken him into meet teachers when no other children are around, showed him the classrooms etc. It sounds like he's had countless members of staff helping/supporting him, they've tried the sensory room (he doesn't like) tried to get him out to eat lunch with a friend (he refused).
Family wise, yes lots of support, very involved DH, older ds who is tolerant but doesn't really understand why he's anxious and as for me I'm on the waiting list for therapy as I've reached the point now where after over 2 years of this I'm beginning to break. Phew another epic post but I do feel slightly lighter already!