According to this link, for the 50th percentile, Aboriginal Studies is the lowest scaling subject with a scaled mark of 12.6/50. In contrast, Drama has a scaled mark of 23.9/50 and Mathematics Extension 2 has a scaled mark of 44.3/50. Depends on your definition of scaling, tbh.
It doesn't scale *too* badly, it's normally around 23/24 average scaled mark. Aboriginal Studies, CAFS, general math and senior science and some othe subjects are worse.