Doing well in units 1/2 mean next to nothing, a lot of the content in 1/2 is not related to 3/4 at all and the rest is only tangentially relevant in the subjects I am aware of. The only subjects I can think of where 1/2 would be fully relevant to 3/4 is maths, because maths is essentially just building up on your skills developed through the years. Putting lots of effort in 1/2 doesn't equate to anything except developing good study habits and entering 3/4 with a solid foundation. To be completely honest, 30 practice exams sounds like overkill to do for all your 1/2 subjects - I didn't even do that many for both of my 3/4 subjects combined last year, and did none for my 1/2s. Doing a few practice exams, going over them and reflecting over your mistakes is a much, much better idea than mindlessly churning out practice exams (which will NOT help you and could lead to burnout). If you really want to prepare for 3/4, then complete all the holiday homework your teachers set you and maybe read over the textbook/get a headstart on the first area of study during the summer holidays. I'm not dissuading you from trying to achieve well in your 1/2 exams - you should definitely aim to do this, but be aware that doing well in 1/2 doesn't mean you're going to do well in 3/4 (in fact, there are a significant number of students who don't do too well in their 1/2s or don't do the 1/2 and absolutely smash 3/4). In the years leading up to year 12, it's all about gaining a good foundation for year 12 and developing good study habits. Like jborn007 has already pointed out, doing X number of practice exams means nothing if you aren't adequately reflecting over them. I would recommend against doing 30 practice exams for your 1/2s and instead do less but increase the quality - mark yourself harshly and get help if you don't understand certain concepts and practise those.