When I read this question, it brought me right back to the time when I was completing my doctorate at Cambridge. I had spent five years, alone, studying a topic that was rather obscure and was about to be assessed by two eminent professors. They had the power to influence my entire future. My viva would last a few hours and, during that time, two people would determine whether or not the last five years had been a waste of time, whether I would spend another year making revisions, or whether I would leave the room as Dr Weston. Your son has also identified that the stakes are high and feels that his future is in the hands of his teachers.
The fear of failure can lead to enormous periods of procrastination and it can also be completely paralysing. Sometimes, it is easier to simply stop and withdraw from the process. I get that. Anyone who has climbed a mountain and looked up mid-way through, will know that overwhelming feeling of doubt that you’ll reach the top. However, by focusing on our feet taking each step, rather than the top, we can help nudge ourselves gently and successfully towards our goals.
The answer to your question lies first in helping your son to take some deep breaths. Perhaps you can share the mountain metaphor with him? Coach him by mapping out each subject. Look at it on a big piece of paper. How am I doing? What do I need to do and when do I need to do it by? What positive feedback have teachers I received about my work? What do I need to do to improve my academic outcomes? Teachers never want students to struggle and have empathy for the situations that they find themselves in. Encourage your son to talk through this mini-audit of each subject with his teachers, and seek their advice on next steps. Help your son see that he has a plan, is making progress and that teachers are always allies when it comes to work and study strategy. No one wants him to do badly.
The positives in this story are that he cares deeply about his work and future, he has parental support and his teachers clearly care and want him to do well. By gently helping him to acknowledge his anxiety and take small, achievable steps, he will slowly see the light at the end of the tunnel.
If you don’t feel comfortable being the ‘coach’ in this situation, you might consider getting him one in the form of an ex-student who has studied the same subjects previously (for some tips and moral support) or hiring an academic coach, just to mentor him through this tricky period help him to organise his work better. It might also be that his peers or a particular family member can help by chatting to him once a week about what he has achieved, and what his plans are for the next week. Lots of caring, scaffolded support is the best option at this time.