Definitely year 11 then year 12. He will be a touch older than most others in year 11, but I don't think that will be an issue. Secondary school is year 7-year 12 and they do their hsc exams at the end of year 12. We start our school year in late January here. I would expect that he would start next year, if you're moving late this year. Year 11 (preliminary course) is term 1 to term 3 and then they start on the hsc course in term 4 of that year.