Its' difficult to pick high schools based on location now - as things can change and somewhere that is 'good' may not be 'good' in 5-6 years time (though your 'great' ones such as Glen Waverley etc should maintain that 'reputation'). Also people within an area are often more negative about a school then people a little out of the area as they hear more negative stories. I can't imagine how difficult this is for you! Just keep asking and asking and you'll start to build up a little mental map of suburbs/schools and whether schools are good or not.

Another idea is to make the acquaintance or ask teachers that are in the areas you are looking at - I know that in primary school the schools are in networks and the teachers seem to know a bit about schools in that network and I have used that information to hear about schools that are not 'great'.