I have never been asked to demonstrate or prove my educational details.
I did very well in Maths and English, so have nothing to worry about, I guess it depends a bit on your age.
If you are entering the job at their minumum age requirement, then they might look at it more closely. Most airlines take people at 21, which is stil rather young - only out of high school for a few years. Some even take people on from 18, which is a bit too young in my humble opinion. It is very unlikely that an 18 year old has the life experience and maturity to handle the demanding and complex situations of the job. I'm sure that there are a few very talented 18-21 year olds out there though, good luck to you all.