"Realistic" goal setting always messes with my head. Unless you're a perfectly objective agent, how do you know you're being objective? Fact of the matter is, there is no perfectly objective agent, so teachers etc aren't much help either unless they have an extremely good grasp of your abilities and potential. Feasibly they could grasp your abilities but it's near impossible to evaluate someone's 'potential'. Like, there's a huge issue with this 'realistic' goal setting because any goal you set is going to be arbitrary. "Yeah, 75 is realistic!" Then why isn't 76 realistic? And if you make room for 76, then why isn't 77 realistic? And this goes on forever. It took me until after high-school to fully realise that goals in high school are a bit weird. Like I was aiming for 90 and ended up a few points above that, even though I expected about 85. I tried to aim beyond realistic anyway and I STILL outdid my "beyond realistic" goals. If I could go back I'd just aim for 99+ even though it would be obscenely difficult to achieve given the amount of subjects I did and my score in Year 11. Obviously there's little chance I would have got there, but I probably would have worked differently if that were my aim. That's why I think if you're aiming high, there's nothing to aim for except for 100% on all of your tests etc. *I didn't say ATAR. Your marks on tests aren't dependent upon other people. You can control your test marks. You can't control your ATAR because it's dependent upon how well or badly other people go etc etc. So I wouldn't bother with ATAR aims. I'd just say "I'm going to aim for 100% on everything". You won't always get it, you might not even get it once. But at least it makes logical sense to aim for 100%. Anything else is arbitrary. And at the end of it you'll be left with the best ATAR you were ever going to get given your particular set of circumstances (not the best ATAR possible for you, because theoretically something could always have been better, but you'll definitely get the best ATAR GIVEN YOUR SET OF CIRCUMSTANCES if you aim as high as you can, every time).
Your grades are 80-90%. But you could do better, couldn't you? You could study more efficiently. You could study more. You could take more effective breaks. Ergo - just aims for 100%, or as best you can achieve (which is 100%) and let the chips fall where they may.