I want to enter a conservatory to study (I'm 20 and living in Australia). I don't know where music could possibly take me in a career but I feel like music is the only thing I want to study.. ANYWAY, what piano grade do you think is needed to successfully enter a conservatory?
It's not related to a grade, it's related to the audition you will be asked to pass.
Whatever grade you had before, music schools will assess for themselves wether or not they want to teach you, and that depends on your musicianship, not some grade.
No honest answer with a grade can be given. It just doesn't work that way. Someone getting 60% in some high standard school could succeed easily an audition, someone getting 100% in a children school could be refused. Some schools don't even use grades.
What you can do, is directly ask the conservatory what the general level of their entry level students is, generally in terms of "you should be able to play the eight year level of this popular school program".
It's going to be a minimum grade VII going on grade VIII. On at least one instrument, probably another grade on an extra instrument. But there's a lot more: the audition will reveal what level you're at as a musician, something that a piece of paper saying you passed an exam cannot do. they're also looking for other qualities, so even gaining a grade VIII distinction will not be enough on its own for entry to some conservatoires.