From my understanding of those courses, in Ancient History and Visual Arts you shouldn't be relying on any one study guide or textbook. The same is true for English regardless of the level. You should be analysing the prescribed and related text yourself or with your teacher's guidance - a study guide will not ensure more than the minimum results as opposed to direct analysis. Regarding the other two, well I hear Heinemann is good for Senior Science and I think the General class at my campus uses the Maths in Focus for that... http://hsc.csu.edu.au is also a valuable resource for most courses