My teacher told me that score around 150+ overall so you can score an A.
But I couldn't understand how do they mark the paper. I appeared in June'08 exams. I've lost almost 50 in paper-1 and about 15 in paper-2, leading to an expected score of almost 135. I am pretty sure that I have no less than 130. I got a lower-D at 64%.
Though, my teacher had sent my expected grade A to CIE, keeping in view my academic record, which was almost and always 160+.