I agree with everything Sweetbun says about the industry and especially If your son is gifted, maybe he's just bored but it's good to learn that you have to work through your boredom to succeed in the workplace. Ds2 is year 10, he is also bored shitless of English lit but he still has to take his GCSE in it. 
Yes you can leave school at 16 (end of June) but the rules are
You must then do one of the following until you’re 18:
-stay in full-time education, for example at a college
-start an apprenticeship or traineeship
-spend 20 hours or more a week working or volunteering, while in part-time education or training
That last one isn't clear enough it means no one can employ a 16 year old full time, they must complete at least 280 guided learning hours a year in education or training. If he has an offer of a job at 16 it must come with training too.
I would think that something you love now at 14/15 may be great but he needs at least GCSEs before he can move onto anything else. And yes, my son also codes/does ethical hacks/does online courses/has certificates for completed courses/completed uni summer schools for CompSci and has been doing that since he was year 10. So I do understand a child having a massive passion for something.
But he also has incredible GCSE results, is year 13 and should walk with 4 stellar A level grades and has 4 offers from top RG unis for CompSci degree.
Because as Sweet says it isn't just about coding it is understanding how that fits into everything else and also uni courses cover a wide variety of disciplines, AI, Data Science, Networks, Computational thinking etc. Just because you love something now doesn't mean you won't change your mind especially if you have been introduced to stuff you haven't even considered before.
As a minimum he needs to stay on for his GCSEs, has to in fact.