English std definitely will if you are aiming to get that atar especially, you need to do advanced. Unless you are getting a band 6 in Std, it is a lot harder than it sounds. only 56 people out of 34 000 or so get a band 6, compared to 3000 or so out of 33 000 getting a band 6 in advanced
If you are strong in maths and science, that's good. However chem and physics is a little jump above from year 10,there's lots of stuff you haven't covered before in year 10 such as moles, concentration,trends and year 12 there's even more to add on top of that. I'd say physics is a little easier with some background knowledge from year 10 than chem is
maths is going pretty fast in year 11 and year 12 esp for ext 1 & 2, and I guess it's harder and even harder in year 12 esp for 4 unit maths. However, getting a 50% in 4 unit maths isn't going to get you a 90% scaled, because it is actually going to be maybe 68-70% at best. Even though it's high scaled, you need to do well in it to be in your favour (at least 70% raw). Otherwise you're better off doing a 2unit math and 3 unit math combo because 2 unit is pretty easy and reassuring if you are unfortunately bombing your other subs.
What is your 12 units in prelim? You need to do 12 in year 11,currently your list only gives 10 units,presumably for year 12 study.
