Its more about managing time properly, i have a good 7'ish hours from when i get back from school and when i go to sleep, ~4-11:30'ish. There is no way in hell on an average day i'm devoting more than 3 hours to homework MAX ever, so that leaves me with 4 hours chill time, saying giving half an hour for dinner that's still 3 and a half hours of free time in which i can watch up to 10 episodes of a ~20 min tv show which is WAY more than i actually watch.
Pre-exams, say 1 week before major exams i work about 4 hours a day still leaving me with an absolute minimum of ~3 hours of spare time.
Also i do go to a selective high school so it's not like me and all my friends are going to fail
The couple of students that did try and basically do nothing but study starting from the prelim HSC basically all burned out by the end of year 11 and started getting crap marks.