This. Never EVER do Standard. Tbh, I can't tell the difference between Advanced and Standard.
Standard and advanced english are almost exactly the same in terms of difficulty so I see no point in not doing Advanced even for bad performing student. As I said previously it will do nothing but help your atar. Also, I recommend you move as well.
IMO I believe English Standard is a lot easier than Advanced, especially for someone who isn't passionate about English, or isn't particular good at it (seems kinda obvious). I managed to get a band 5 in Standard ; which would have been unlikely If I had done Advance. But by hypothetically substituting my Standard mark for Advanced in an ATAR calculator, it only made a 0.15 difference, which wouldn't really have helped me (could of though!). So unless you want/need an ATAR above 99 , choosing Standard can be a good idea.
Anywhoo. Back to the OP, like everyone else has said, 1 subject could easily bring your ATAR down, but If you put your head down and keep trying hard, you can definitely get over 94. I was in a similar to position to you in that I failed my first Standard assessment worth 20% (I really shouldn't have, it was total BS) , so was totally gutted about it since my ATAR aim was 96+. Eventually I got over it (was pissed off for ages though) and decided to spend a little extra time studying (didn't want to neglect my other subjects) English and ended up 1st LOL, not only because Standard is not that difficult but also because hardly anyone tries, so getting a good rank is a piece of cake. I know it won't be like that for you, since you're in Advanced, but the point is, that it is possible for you to bounce back! Consider a tutor as well, that could be the boost that you need.
Also if you end up not getting the ATAR you need, it's not the end of the world (which you've probably been told 1000 times).... I didn't get the ATAR I needed (although I did get 96.3 which was my aim lol ><) but after studying in a different but similar course, I got the marks I needed to transfer to the course I wanted... just focus on studying and doing your best, that's all you can do really, don't worry too much!
So In conclusion, Good Luck and Peace Out