I've extracted some more data from the Chatswood and Fairfield areas regarding high schools, and applied it to my favourite graph - the one showing how the NAPLAN scores of schools improve over time. The problem with this data is that it's not continuous - you have kids going from primary school to high school, so there is a break in the data between years 5 and 7. On top of that, NAPLAN testing hasn't been going long enough to follow the same set of kids from grade 3 all the way to grade 9. The results for years 3 and 5 are from a different set of kids from years 7 and 9.
No matter - we just have to work with what we have.
The bottom axis is the ICSEA score - a measure of wealth. Poor areas to the left, rich areas to the right. The blue data points are the NAPLAN scores in year 3, the brown ones are the scores in year 5 etc etc. You can see how the NAPLAN results climb over time.
What surprised me is that the rich schools pull away in high school - particularly the state schools. There are a lot of very expensive independent schools on the North Shore, and the elite state schools leave them in the shade. More on that another time.
Have a look at the results of the school in the red circle. What you're looking at there is the NAPLAN score for a Fairfield school for its year 9 students. The long red line shows where it sits in relation to state schools in a rich area. By my reckoning, kids in year 9 at that poor school are at about the same level as kids in year 4 at the schools in the rich area. That's the difference between a state school in a good area and one in a bad area.