You'll probably maintain it, alot of the prelim course builds onto HSC course, you'll actually see subjects numbered, and they start 1-4, example PB1/PB2 = prelim, PB3/PB4 = HSC, if you don't know PB1/PB2 you're screwed.
However, be very careful, a lot of Mathematics (and even Extension 1 Mathematics in our school) drop down to general and annihilate everyone. You may be up for some serious competition, if you want my advice, do
all homework, and over summer holidays study ahead, learning maths twice helps it drill it in.
My mates sister got 97 for General Maths and she finished entire maths course by the time it was half yearlies and was doing just past papers from then until the HSC.
Good luck