My school was similar to yours; we have a cohort of 240 people but only 40 people were accepted, minus the people leaving which was around ~5 people. Most students, even the ones that were considered smart were placed in standard. Of course, we protested and argued which allowed the number to be about 43 or so... still pretty bad considering my school is top 100 and our cohort is capable. The moral is: do whatever you want to do. The teachers may think they know your capabilities but not their potential.
My advice to you is to take advance. I'm pretty sure they cant force you to take standard; correct me if im wrong on this one. If you're taking biology, chemistry, physics, SOR, extension maths i'm assuming you're already a hard worker due to the high demand those subjects require; if so, why stop your boundaries? Theres comments that say 'only 0.01% get a band 6' whilst '11% attains a band 6 in advance english', which is true. But the bare minimum band for a 90+, considering youre doing well in other subjects is a band 4 and the numbers of band 4-6 is atrocious for standard, i mean only approximately 34% out of about 30,000 students attain a band 4-6 (thats approximately 10,200 people) that whilst about 80% attain bands 4-6 out of 27,000 students (thats 21600 people) - 2013 statistics
Now im not saying that if you undertake standard english that you're doomed to attain a rubbish atar, i know plenty of people who got 90+ with standard english. I'm saying that statistically, you have a higher chance of attaining a good atar if you coupled your subjects with advance english. I know that a couple of BoSers will back me up on this. Good luck!