I go to a selective high school, and there were no subjects (which had a preliminary course) which you could pick up in Year 12. But, there was an instance where a guy did SOR1 at Tafe in Year 12 (ie. out of school ours) and managed it well, iirc.
With SOR1, only the Depth Study requires you to have a background knowledge of the Preliminary course, eg. Buddhism with Puja (Prelim.) and the Wesak have interrelations.