generally the economics stuff you do at HSC isn't the "nuts and bolts" of economics and is usually focused on empirical evidence/studying real-world economics (i.e. what happened to the american economy during the industrial revolution/depression, etc.)
you'll find because HSC incorporates micro, macro, economic history, what you learn is very basic and is just scratching the surface.
also, all uni's will teach micro 101 in a relatively simplistic fashion, such that EVERYONE starts on the same playing field, and you work your way up. they don't tend to do many proofs/derivations, so they go "the demand curve slopes up, take it as it is and don't question it till next year". which is good i guess for first year students.
that said, i have 10 or so mates who didn't do economics in high-school and got 70%+ in micro 1. micro 1 is an INTRO course, and is intended for EVERYONE to pass (of course this is based on the assumption they put some effort in). if you failed micro/macro 1 you're pretty much a boob.