Summer school is AWESOME. Enough said.
The chemistry summer school was two weeks in which you cover the whole of first year chemistry and some extra topics from second and third year university chemistry (following the UoM syllabus at least). You have a prac, 3 lectures, 2 tutes (I think) everyday.
It was an awesome two weeks. My only regret is not getting enough sleep everyday. I'd do something similar again, definitely. If you get in, I highly do NOT recommend refusing the offer to go. You meet great people, you stay away from home for a bit, the food isn't too bad and you just get to have lots of fun in general. It really is a once-in-a-lifetime opportunity. I reckon bio and physics would be equally as intense.
Plus, it really helps with VCE and puts the difficulty of VCE in perspective.