The results you get from school will only serve to get you part way to a Scholarship...
You don't need to be clever to be a Pilot, all you need is dedication, determination and hard work.
I left school at 16 (always wanting to fly) with no qualifications!! I joined the Army as a private infantry soilder (4 years). Then went to the Prison Service (7 years). Now that gave me life experience, I left the prison to start flight school and never looked back.
OK the groundschool was hard with no academic background but hard work and determination is what counts, it pays off in the end.
Now I fly a twin turboprop all over UK and Europe and am building my experience nicely.
So do your best but dont get too bogged down with exam results.