GCSEs have been in place since the mid-80s, are pre-16 education and count for somewhere between fuck and all as far as college/university is concerned
when I did them there were no preset grade boundaries (IIRC the passing grade for maths was ridiculously low, something like 21%, so that the government wouldn't be embarrassed by the fact the vast majority of high-school pupils had no fucking clue how to pass it) but as I said, my knowledge of the education system is 20+ years out of date, and it's almost certainly been turned upside down since then
Well GCSEs qualify one to do the further education which in turn leads to university or what this known as college in North America.
So they have a bit of bearing, especially if one wants to get into a top tier school.
The major changes I would say in the past 25 years was introducing numbers instead of letters for the grading system, and splitting a-levels up into two one year courses rather than a single two year course.
If I remember correctly, it is A levels that are most important now for Uni entrance in the UK, and you need certain A-level grades in certain subjects for certain majors, and certain universities. But I'm sure that has all changed since I know it from a while ago.
A levels are the most important for university entry and have been certainly since the 50s or so.
As a rough rule of thumb you need A-D grades in a-levels to get into any respectable university, and the subject needs to be relevant to your a-levels. E.g. if you want to do a science, biology, physics and mathematics are a safe choice in a-levels. They won’t let you do molecular chemistry if your a-levels were in dance, art and literature.
Oxford and Cambridge, and maybe more famous universities, have their own entrance exams, so one needs good a levels and to pass these entry exams.
The posh schools, Eton etc, specifically run lessons for those exams, which state schools typically don’t. So if you are a normal person you need to either be shit hot or pay for private tuition in those exams.
In any case fat might have ended up with a slightly better GCSE response as one or two have a higher percentage of the final grade based on an exam.
If he struggled with maths though, he would have been placed in the bottom tier and only been allowed to sit an exam which would get him a d grade at the very best.
Ultimately this would mean that he probably wouldn’t be able to sit a-levels, so would certainly struggle to get into university, unless he waited to his mid 20s or so and tried to enter as a mature student.
By then though, knowing Pat, he would have convinced himself that he is too smart for university and would scare the soft spoiled students due to his manly odor, I mean aura.