GCSE revision help

I'm a mother of a 15 year old boy with Aspergers. He will be taking GCSE exams in May next year and I am struggling to get him motivated for revision.

hes recently taken mock exams and knows what he wants to do, but is barely passing and I’m extremely worried as he has had issues with mental health due to exam stress, bullying and anxiety. Obviously he’s very bright but he won’t revise and it will become a vicious cycle - not revising, not passing exams which then makes his mood very low and the anxiety and mental health issues return.

Any advice or feedback would be gratefully received. He is a very clever and capable boy and I keep reminding him of this