I am actually from the YSA (Young Scientists of Australia) and we staff these schools every year. I actually recognise Cherylim's username from the YSA forums.
The Science Experience is a 3 day program at a university where you get to go to lectures, labs, excursions, tours and many other things so you can learn about science. However it's not just about science, certain schools run trivia quizzes and team building exercises as well as discos.
It is a great way to meet new people who are interested in science and if you do UoM or Monash TSE, you'll get to meet the YSA who are basically a youth group interested in science who have monthly meetup and such.
I highly endorse doing it, I never got to experience this as a student however I have staffed 4 of these so far and it really has expanded my horizons. (I actually just got back from a National Conference in Sydney discussing this).
If you want to know more about it, feel free to ask (preferably via PM)