If he’s an able student, the school should be directing him towards the academic subjects. That’s what would happen in a selective school.
You are right that people need to study business, psychology etc.... yet the time to study them isn’t GCSE. GCSE is for a broad based curriculum which keeps doors open. Even A Level isn’t the best time to study the subjects you mention, for an able child. People go onto business degrees, psychology etc without having GCSEs or A Levels in them.
The GCSE profile which is regarded most highly is a decent number of subjects (8 is fine) with the majority being standard academic subjects at high grades.
Remember, you can’t do History A Level without the GCSE. You can do business. You won’t do a History degree without A Level. You can do business.
When choosing GCSEs lots of children are attracted to new exciting real world subjects that look more exciting than the subjects they already know. They tend to be taken by the less able students who have struggled in the standard subjects (not in all cases of course) and are less well regarded for academic rigour. Look at if your nearest independent or grammar school offers them...probably not. Most won’t offer business at GCSE and only some offer at A Level, but offer Economics instead.
Get your son to have a discussion with the careers advisor at school about which options will keep most doors open and give him a better profile. He needs to hear the reality of the situation and so do you.
It is exactly this kind of thing that lots of Comps are getting critisicised for. They are not directing their able students towards the courses which keep the doors open to the more academic options at the next stages.
Business is a fine GCSE for some students. Obviously GCSE is very basic level and having a GCSE in business isn’t going to turn you into a business person.
Having said all this, I would also say that for an academic student, having 1 GCSE in their profile which is something they chose for interest and which isn’t academic is absolutely fine, as long as the rest of their profile shows them as academic.
So if he has a good academic profile (perhaps 3 sciences, a language, he has RS) then having one subject that really appeals to him (maybe business) is fine. But recognise its worth choosing for that reason rather than its a good subject to study because we need more people with business and that it isn’t a subject at GCSE that ‘leads somewhere’.
Think to the next stage. From his GCSE choices, which A Levels will be open to him and which won’t? Which A Levels might he be likely to do? If he has any idea about degree, are there any requirements or subjects that would be required or good to have.
Hard to think of all this when teens rarely know what they want to do next I know. But essentially I think you both need to understand about keeping doors open and closing them and which subjects help with this.