Do you mean the SC Trial for science?
Year 11 Biology is interesting enough, it's not completely boring. In my opinion, anyway. People often say that Biology isn't one of the more difficult science subjects and it isn't to some degree. But there is a lot of content involved in all the units and you have to have at least a decent understanding of the concepts, which often have links with other units.
Personally, the most interesting topic in Yr 11 Bio was Patterns in Nature, but yeah, the HSC course is more interesting to learn. Choose it if you wish, and if you enjoy the subject. As long as you work hard and consistently - particularly in Year 12 - then you'll do well. And if you're considering studying science at uni, biology is often a prerequisite.