Personally didnt do economics at high school and at uni they teach it right from scratch through macro and micro. Interestingly enough out of the people i know who did hsc economics said they did worse at uni economics then the ones who hadn't like myself, as they complained it was more numerical and less theoretical then at school. However that is just a small sample size of people, but no you wont be disadvantaged by not doing economics because everything is taught from scratch.