Agreed.
During ATPL exams I remember a little GCSE level trigonometry in General Nav and some very basic algebra during Theory Of Flight, other than that, it was junior school level mental arithmetic.
Flying on line; some addition/ subtraction required to fill in the tech log and check a manually produced load sheet (I use my iPhone calculator for this) and in the the air I have only ever needed my three times table for descent planning and the ability to either multiply by five or if that gets too tricky, divide by two for non precision approaches.
A Level maths will look good for cadet scheme applications.