You can drop from advanced to standard at the end of year 11 and in the first few weeks of year 11. However, going from standard to advanced is much more difficult in the first few weeks and near impossible at the end of year 11. Just give it a go protract, it wont harm your ATAR as much as doing standard. Believe me, I know many people who picked standard because they hated english and thought they werent good at it, and regretted it when they got their HSC results. I absolutely loathed and hated english as well, but I dont regret doing advanced for a second.