For the aptitude branches (Pilot, ABM, ATC & Int), the maths must be at least grade B.
I have been reminded that a Grade A or B is only available to students opting for the higher level paper.
If at the age of 14 you opt for a safer course with a top grade of C then you will automatically be disbarred from aircrew selection. How many potential applicants have determined to go for an aircrew or aptitude related career at the age of 14?