I think you have been given duff info. I know pilots who left school with nothing and that made no difference to them. Since times are not good in the industry at present, it would be wise for you to complete your apprenticeship. At least then you have a fall back career when you do start flying. The most important thing when applying for jobs is that you have a ATPL(f). You dont need HNC maths, as long as you can do your 3 times table