Also, regarding History Extension, I would see how you're going in Modern or Ancient before making a decision. If you're in the top 5 of the subject, and you're enjoying it, then go for it. Just be prepared for a lot of writing, but you are obviously aware of that. I've researched it a bit and asked my older brother who did it, and he said it's worth it but it's a lot of work. For the new syllabus, there are some changes, but you are required to do your own investigation. Personally, I'm not taking it up in Year 12 because the teacher who is teaching it is really shitty.