I did a corresponance course for Business Studies in 2002 and 2003. I also did eco in classroom environment.
Trust me, corespondance should only be as a last resort. It is soooo hard to get yourself motivated to work and, no matter how well you think you'll stick to a structured pattern, you will put it aside when you start getting tonnes of work in other subjects.
Mind you, its still possible to do well. I came out with an 89 in BS despite corespondance. I had a teacher at school which i also sat down with every now and then.
I dunno who you're doing your course through, but TAFE-OTEN was pretty bad. Like the info was good, but it wont prepare you. So make sure you get copies of practice papers etc. from BOS and other sources. And see if you can sit all the same assessments and tials as those in your school so that 1) you get a feel for proper assessments and 2) you get an idea of how good you are.
But definately give it a try because you're in yr 11. If you don't like it, drop it. While eco is a course which is definately suited to correspondance learning, it can be easy to fall into the trap of not monitoring world events because u aren't able to have class discussions. So make sure u read the papers/websites, go to the Leading Edge workshops (an absolute lifesaver) and buy alternative text books to use in conjunction with the materials they mail you. The Leading Edge Workbook is a really good buy and the Updated Economics books can be great for assessments.
Good luck with the course and PM me if I can give you a better insight into correspondance learning.