Actually I am rather hesitant to share my story because the odds are definitely against you although I also wanted to inspire you.

Coincidentally I was in similar situation as you almost 20 years ago. I did poorly for my O levels,couldn't get into JC/poly and ended up studying for my A level in a private institute. However as many had expected, I did poorly for my A level (E,O,O) and was facing the same dilemna. I had 2 choices then, either to retake my A level as a private candidate or to get enlisted to Army first. That year was 1993.

After a few sleepless nights, I finally made up my mind and tell myself that if there is one single most impt thing that I can do in my 19 years to determine my future, that would be to do my best 100% to make sure that I get into a local university (NUS and NTU). And I told myself that I just need to slog for 8 months from April to Nov and that could change my life forever. To cut the long story short, for 8 months, I will locked myself in my room after school (was in the private school) everyday and did my own self-study, working on 10 years series, etc etc.

My efforts finally paid off when I received my A level result a year later....I did well enough (A,A,B) to get into NTU Accountancy. Today I am doing better in my career than many of my counterparts/relatives from good JCs.

My message is this: You will be wasting your 1 year unless you are prepared to put in everything you got, sacrifice your entertainment/social life for the next 8-9 months and are reasonably confident that you will do well. You have a 2nd chance, but you need to seize it!