Would any preliminary content be tested in the HSC for Modern History?
The answer is no, since the HSC for Modern History is 3 hours with 5 mins of reading, divided into 4 45 minute sections based on the Core (WWI), the National Study, the Personality Study, and the Peace and Conflict Study, all of which you studied between the start of Term 4 last year and now.
However, preliminary content will definitely not be tested, but it can sometimes provide excellent context for some studies you do this year ie. I did Fall of the Romanovs, then Russia for the National Study and Trotsky for the Personality study, so it really helps sticking some content from that into my work for those two aforementioned sections, so for some people, Preliminary content is still relevant even if it's not tested.
Hope this answers your question!
