Hey!
In the reading I've done I haven't seen anything from QCAA tying specific percentages to grades, additionally, even if you did know what grades tied to what percentages that wouldn't give you enough info to predict ATARs given that it's all about relative performance compared to the rest of the state and the information on what everyone's marks are isn't available.
There's no consistent system for what % mark goes to what letter grade but generally above 90% would be A+ and people think of C as being around 50%.
If you look at the way Victoria figures out A, A+ etc. it's dependent on the % of the state which achieves that score so it changes between subjects and years. (e.g.
2019 data)
I again want to emphasise to you that even in states where there is this kind of historical record no one can actually know for sure for ATARs are possible with your scores so far. Some predictions are more likely to come true than others but nothing is a done deal yet.
Do you mind sharing how they were trying to make this predictions about possible ATARs?
I'm struggling to think of what information base could be used to support those given that we don't know average IA grades etc.
I hope this helps!