When I'm hiring a graduate trainee (or an apprentice trainee), I'm looking for academic ability in something that interests the applicant (ideally not accounts and finance) and lots of extracurriculars.
A "non-relevant" background (i.e. a random degree in something the applicant enjoys) generally yields better pass rates in the professional exams. I need to consider not just someone who can do the job, but someone who can pass the professional exams or I'll just have to fire them later, and that's not pleasant for either of us.
Extracurriculars show that the applicant can juggle all kinds of shit, and that's largely what accountancy is. Juggling, reprioritising... I want to hire a busy person who manages to do lots of things.
A candidate with an A in A Level Maths, a first class Accounts and Finance degree and no paid jobs, no volunteering experience, no committee positions within clubs and societies... straight in the bin. I want some balance and some drive. I will occasionally hire someone who has studied accountancy, but they have their work cut out in proving to me that they're a good hire.
Generally, the best kind of accountants never wanted to be accountants, and have a really broad background and different perspectives on life. They come with better critical thinking. They know they start knowing nothing, and I guess feel like they have more to prove, which is a great energy that I can harness. The ones who have studied accountancy previously think they know more than they actually do, and they struggle more.
If your DC is interested in history and is therefore likely to get a 2:1 or above in it, yeah, it's a great choice for someone who might want to become an accountant.
Someone who has an A or a B equivalent in GCSE Maths who could have easily gone on to get an A or a B equivalent in A Level Maths has enough maths skills. They don't have to actually have done the A Level. If they're more interested in something else, they should do the something else and get the higher grade/have more academic enjoyment.
I'd rather see an A in A Level Geography than a C in A Level Maths.