Hey, i was in the same situation as you when i was in year 12... i did biology, chemistry, maths statistics and economics messed up bad and got 4Ds (this was my fault, i was lazy and didn't take A-levels seriously, i treated it like gcses and expected to get A*s again without any work)... but having asian parents, retaking the year was not an option.... so i dropped economics and continued doing maths statistics, biology and chemistry whilst retaking all my AS exams (including the AS economics that i dropped)...I took it seriously this time and recently got my results.. i got B in AS, BCD which is not good at all, but it was a improvement, but its not good enough... most of this is due to the fact that i had 20 exams this summer with no january exams... i reckon if i had january exams, i would have done much better...
but seriously, im telling you from experience, if you are really prepared to overload yourself with exams, you have to be prepared... you have to be well ahead of everyone. You will experience a stress that you have never experienced before. For you, the exams will be more of a test of endurance, not on what you know... exam period will burn you out...
so if you do decide to do this, throw away your social life and dont get distracted, just be prepared... remember, you only have one shot at it now since all the exams are in the summer and you would be in year 13.. and since you're doing more than 1 science, they will ALWAYS, ALWAYS put science exams in consecutive days... the hardest science units are always on consecutive days... there was one week where i had 6 exams..
I'm gonna have to take a gap year and retake around 6 exams and I'm also going to decide to finish my econ A-level and study for A2 on my own, so i'd have a total of 8 exams in my gap year...
The **** up in year 12 is really ****ing me over....