Check out Dr. Eli Lebowitz and the SPACE programme. There aren’t a huge amount of resources on it (I think they may have published a parents book since ) but even reading through the research papers might help. It’s focus is in showing parents how to increase support for kids with anxiety and reduce accommodations (which we instinctively do but they actually make it worse long term).
Getting outside help was key for us. Child services waiting lists, both funded and private have long, and sometimes full waiting lists, since lockdown. We were able to get sessions with school linked psychologist, supplemented with weekly session a with learning support. They kept me in the loop so I could use similar strategies and words at home.
I’m not sure how to express this without sounding very unfeeling, but it hasn’t helped that he is so lazy by nature! So in the long term I’ve been working on building a bit more grit and self discipline. I never over praise the art/writing/test results etc now, (eg oh that’s amazing) but I praise the effort that went into it (you must have worked so hard on that/ I can see you’ve really tried to improve your handwriting/ you studied really hard for that test) and we have a bit more structure around homework and learning - eg writing out spellings that he has to learn 3 times, ticking off things in his homework journal, and referring back to it when packing his bag. It’s instinctive, I think, to try and reduce stress as much as possible, but we’ve found that being firm on homework expectations, actually has helped. There’s no pressure to get good results but a strong expectation to get his work done.
Recently, after a few calm months, we had another flair up, triggered by teacher panicking as the year is nearly ended, and threatening punishments for incomplete homework. Last year we’d have had to approach the teacher, but this year I just gave him a bit more support to get his homework done, checked, packed away and drew his attention to how that reduced his worry and he could now play for the rest of the afternoon (his own strategy would have been to worry all evening, avoid doing the homework til he was too tired, and plunge into suicidal thoughts and be sick in the morning).
Don’t get me wrong : It’s taken time to get to the point that I can step in and put the focus on homework like that. It’s building on trust that he knows I hear his worries, and take him seriously, and that we can do hard things.
Sorry - long and rambling, but the main thing is you’re not alone. And it can get better.