i agree that Granville Boys would be one of the worst. It would be very hard to be a teacher there. Bullying would be pretty bad.
My cousin told me once that Mt Druitt high was in the news ages and ages ago for having a top HSC of 44 (this was not ATAR or UAI) so this might be an equivalent of about 60 ATAR not sure.. this may have been the reason they switched to the UAI/ATAR so entry scores look higher and the reason why uni entry scores are no longer public and available to schools..
In all fairness the good students from Mt Druitt would have probably moved to a better school, like St Marys Snr, or whatever. Which doesnt leave them with much left. The general behaviour may not be as bad as granville boys, they probably just didnt do much work assuming they may not aspire to get into uni.