Well i can tell you that just cause you did badly in prelims doesnt mean you'll go bad in yr 12 if you put in the effort.
I have moved from 30th in maths to 2nd
30th in phys to 2nd
70th in chem to top 15
and english 130th to top 50th atm.
and yeah i paid no attention in yr 11, but it helps to know whats going on.
So either, muck around and try your absolute hardest in year 12, or start getting into a routine now..
Like if you muck around, when the basics are needed...valencies, balancing, dispersion forces etc, i didnt know them, so i had to go back and revise what they all meant..
tbh, i dont reckon i could recall all the different forces between molecules now, without looking in my book..