Primary (Years 1-6): Australian schools typically suggest 10 minutes per year level. So Year 3 = 30 minutes, Year 6 = 60 minutes, a few times per week.
Secondary (Years 7-10): 1-2 hours per night is typical. Varies by subject and intensity.
Year 11-12: Significant study and assignment time—often 2-3+ hours per night, especially as exams approach.
These are guidelines, not hard rules. Some schools do less, some more.