To teach a subject, you need to understand it, and understand it well.
So no, it's not acceptable that a class at GCSE level is taught by someone with only A Level or equivalent qualitfications. No, Maths should not be taught by someone with a Politics degree. Actually enforce standards on the teacher qualifications that mean something.
Kids need to be taught Science by people with Science degrees (and preferably someone who earned above a third in the respective subjects). Across the board, so yes I include the humanities in this.
I once had a GCSE science (Physics) class taught by a History teacher for a month - we learned nothing. Thankfully that wasn't the norm and the class did well in the end.
But if politicians admitted that, they'd have admit they're utterly unqualified to be making decisions on their respective 'committees', especially as those have real world consequences.