School anxiety

My son is in year 4 and has always enjoyed school. However, he has always struggled with maths. To some extent, it is a confidence thing, and because he doesn't like the subject he's approaching it very negatively. He had a tutor last year (who sadly went back to full-time teaching so we are currently looking for another*) who said he was much more able than he appeared.

At the end of last term, they did some end-of-term testing and his teacher called us in for a meeting because he got the lowest score in the class which she was surprised by as in reading and spelling he's scoring above the expected level.

During the meeting, in which my son was included, we had a quick look at the test papers and he was able to answer some of the questions he'd got wrong when just casually looking at them.

We then went into the Christmas holidays and he started stressing about going back to school shortly after Christmas Day. Since then he's been having trouble sleeping, coming into our room early hours wanting to talk about school and not just math, it's spread a general anxiety about all elements. Complaints of tummy aches and not feeling well.

After the meeting, his teacher did say it was a wake up call for her that he needed some more support, but that he wasn't the only one so she would be creating a little group that could get extra support which has happened. We've told him to speak to us if he hasn't understood something during the day and we'd go over it which we've tried to do - we've got copies of the work sheets they've done to go over them with him.

Has anyone had kids dealing with similar issues? Any suggestions? It is pretty upsetting to see him getting so stressed about school at this age.

(* surprisingly hard to find someone who will do in person and since he doesn't even like speaking to his Grandparents on video calls, I don't think virtual is an option).