How much can externals raise my atar (1 Viewer)

[Panda4321]

HI i was just wondering how much external could raise my atar. My subjects are
English as second language- 2/12 (88%)
Chemistry- 4/26 (87%)
Biology- 25/84 (80%)
Maths extension 1- 9/25 (77%)
Maths Extension 2- 5/7 (57%)
Physics maybe from 16-19/29 (don't the average % yet but should be around 60-65)

So how much can the externals save me? Can i get about 90 ATAR cuz right now it seems i'll be getting around 80
Thanks in advance

 

[teridax]

School rank?

 

[Panda4321]

the school ranks' 147-149