A-levels are looming, my DS is struggling

[PerspicaciaTick]

My DS is in y13, with A-levels about to hit him.
He is taking Maths, has always done pretty well and is predicted a grade B.
But with every term time test and now his mocks, his grades are going backwards and his confidence is sinking.
And now he is starting to freeze in exam situations.
He won't talk about it and seems to struggle to sit down and tackle the issues head on.
How can I help and support him to rebuild his confidence. I'm worried about his MH and am concerned that more pressure will make things worse.

Could he have a processing issue making exams tough? Does he need exam adjustments like rest breaks or extra time? These things often become visible in 6th form when demands of curriculum make them hard to mask and cope with.
ask some questions of the school. Ask if he needs to be assessed.

Talk to his maths tutor. Do you have a parents' evening? They should advise you on how to help, which areas he needs to work at, and provide past papers.

Can you find a local tutor to add a bit of supplemental time, and restore his confidence?

Ask for a meeting with school.

Can you afford a tutor to help with exam practice?

We had a parents evening just before Christmas. His tutor seems confident in DS' ability so didn't really make any suggestions.
I think a private tutor might be something we need to look at, if DS can be persuaded to engage.

Go to Spire Tutoring and pay for a few online sessions. I have no affiliation. DD’s grade improved significantly.