Anyone who passes all the ground exams first time is either:
a.) lucky
b.) Too clever to be an airline pilot.
I know this because I am extremely clever and I actually failed a couple myself.
Seriously though I think that first time passes and average markings are just used as another filter in the airline selection process.
I think probably about 70% of the exam material is forgotten never to be used again as soon as you walk out the exam room. I think the airlines probably know this as well.
cheers
MJR