I would recommend Student Answers for the SC series which show low-range, mid-range and high-range answers for past School Certificate exams. Otherwise the next best thing is your updated exercise books that you use in class.
*Lol I've been unintentionally promoting these books for many threads!
I wouldn't bother with study guides for SC. They are really unnecessary provided you have textbooks for the subject and access to board of studies site to do previous years tests.