We had a 15 mark question in our exam, made out of two parts, draw the information, then do a proof. The proof was 15 marks, no real lead in. That was a bitch of a question.
If you're the only one in the class, it just means that your HSC exam mark, no matter what, wil be your HSC assessment mark, so that your HSC mark will be the same as your HSC exam mark. Basically, your mark in extension 2 maths all depends on you.
Oh, he's around average rank, and the school does alright in the HSC exam, around 10-20 a year gets band 6 in the external HSC exam for 2 unit maths :)