Short answer
Home Affairs looks at your personal situation, immigration history, study plans, and whether you are likely to follow your visa rules.
Home Affairs looks at whether you genuinely plan to enter and stay in Australia as a student. It may consider your personal situation, immigration history, and the reasons for your study.
If you are under 18, Home Affairs may also consider the intentions of your parent, guardian, or spouse.
Home Affairs may also look at whether you are likely to follow your visa rules. This can include your past visa history and what you say about following the rules in future.
Each application should be considered on its own facts, including the information and documents provided.