I agree with Whirlygig - school maths and physics are far beyond ATPL standard, and cover an enormous amount of material which isn't in there.
Another thing, as indelicately put by Aussie John, is that ATPL writtens are multiple choice, based upon memorisation of material. The CPL/ATPL flying content is then specific training for a job.
This is a big difference from education - building of understanding and learning skills over many years, which is what a schoolteacher is doing.
Personally I found my first degree (in aeronautical engineering) much tougher than my CPL writtens, and also requires very different learning skills.
Also, I'm sure we'd agree that ATPL flying shouldn't be taught by somebody without more than an ATPL alone. So, why should a school allow maths A-level to be taught by somebody who hasn't gone well beyond maths A level themselves.
Frankly, I think that the only way ahead is to do a first degree in a numerate subject - maths, physics or engineering. The good news is that you can do this through the Open University in your own time. If you really do have degree level skills, then it'll be quick and easy. If you don't, then you needed to do it anyhow.
Sometimes, you just need to jump through the hoops! I've never heard of anybody with a degree in Aerospace Engineering being let of PPL/CPL/ATPL written exams in any of the technical subjects - but I doubt that any of them struggled much either.
G