infinitely more useful as a subject than Geography or History ( from the point of view of running a future vet. Practice)
It depends a lot on the area you end up working in. I admit I can't see how these would be useful for running a vet practice, but in marketing if I had to single out one degree that I have found over the years to be the best preparation, it would be geography (and this is a popular degree among employers in the field). It doesn't sound obvious, but in practice they prove to have the right skills, mindset, and often have done remarkably similar projects. (The ones that apply usually have done at least some human geography.)
History, which a few people have referred to as impractical, has come a long way from the days when it was just memorising dates of battles, and now some are doing a lot of research, writing, analysis, conclusions drawing, and these people can have some really good fundamental skills and abilities, although the issue with history graduates is that they usually aren't numerate enough. Even this is changing though as I think there is a trend towards using quantitative information sometimes.
A lot of it is about the underlying skills and education, which sounds waffly, but does really matter. The "practical" and business skills we are very well able to teach them at work, and will have to do so anyway even if they have already taken these subjects. Abilities like writing, understanding and using numbers, having the potential to interpret information and draw sensible conclusions, are much harder if we haven't got a solid base to work from. In the 1990s (looking old here!) it wasn't a problem, but since the early 2000s, it's been a big one.
Going back to the original poster, as long as your son isn't giving up academic classes he might as well do something he is interested in. I took business for three years in high school, and although the impression that it was going contribute to my progress in this field was really illusory, at the time I loved the feeling that I was already doing something useful on my chosen path, and it was very motivating. I did get a lot of pressure to take extra science classes instead of business, as bright children were expected to go this route, but I was firm about the direction I was going. (And ironically, I got accepted to MIT which nobody else in my school ever did... The value of working hard because you're motivated and interested.) Business studies sound a lot more interesting nowadays anyway; I would have loved cricket balls' class.