優(yōu)選答案If you intend to enter the university directly, you definitely need IELTS for 1) Visa purpose and 2) university admission.
However, if you come to Australia when you are below 16 years and join high school here, you may not need to do that. Check with agents to see which is the best way for you. If you join high school, you'll compete with all the students for the places in the university of your choice.