I struggled with 4 CSE results , 2 three's and 2 two's up to the 5th year. Teachers couldn't work out why as it seemed I wasn't really trying. I still have some of my report cards which say as much, 'capable of much more if he put his mind to it', 'lacks drive', 'More time working & less time playing around' that sort of thing.. After many trips to child psychologists didn't improve results, they did an IQ test, not that high by all accounts but high enough to qualify for MENSA.
I had the school deputy head living on one side & a science teacher the other & during a New Year party, one of them noticed nearly all my books were science related text books. They worked out that most of the stuff being taught in my lessons, I already knew, so I just switched off. The only subjects I didn't know were the ones I did well at come exam time. They convinced my dad who was ready to throw me out at 16, to let me go to 6th form, which I did. I got 6 O levels all A's and B's (although I failed statistics miserably, just no interest in the subject), mostly in science related subjects as O levels were more challenging & actually taught me something I didn't know.
I've since gone on to get a couple of A levels in sciences and studied Cosmology & Planetary Sciences and Astronomy with the open University. I have a few work related diplomas as well.
I've often thought what would have happened if I'd actually worked at my education through years 1 - 5. Would I have done any better or worse. The truth is probably not as from when I left school at 17 until I was 27, I did as little as I could get away with, signing on most of the time, working a little here & there when I had to. The experiences I picked up at the 'University of Life' definitely helped me see things for what they are, something I feel is lacking in many people today.
If my exam results were based on my mocks, I would have got better grades and quite possibly been a different person to who I am now (no intervention from my neighbours & kicked out at 16), but getting lower than expected grades definitely wasn't the end of my life & it didn't ruin my future, it would have just been different.