Not exactly true for the last to parras. Private schools (GPS ones at least) have a significant emphasis on cocurriculars, to the point where they force students undertaking programs. In the case they don't attend before exams (fyi these programs are run after school on mondays), they can be vulnerable to lose %ages out of their hsc exams. Same goes for sport if not attending trainings or saturday sports. There are also much more international application assistance in these schools (mine especially for some reason runs programs specialising specifically on just this and have found heaps of success, getting students into oxford, cambridge, etc). In terms of clubs, heaps are available, and you are given the opportunities to put forth new ones if you have evidence students would be interested. In terms of being bogged down after moving in yr 11, I did not feel much of a huge difference moving from a 140th ranked school to a top 50. This is maybe because I switched from coed to single sex education so take this w a grain of salt.