The brouhaha over My School is an important lesson for those of us interested in geography because it demonstrates how misleading a reliance on average values can be.

In a previous post, Limitations of My School, I pointed to some problems with the Index of Community Socio-educational Advantage (ICSEA) used on the My School web site. In particular, I was surprised to find that prestigious Melbourne Grammar scored much the same on ICSEA as nearby State school, Camberwell High.

This unlikely result was because each school’s ICSEA rating is calculated from the social and economic characteristics of the Census Collection Districts in which its students live.

Camberwell High School

The problem is that although the average socioeconomic status of Camberwell and surrounds is very high, there are nevertheless significant numbers of residents whose incomes don’t extend to finding upwards of $20,000 per annum in post tax income to fund a private school education for each of their children.

In other words, Camberwell High ranks highly on ICSEA because its students live in ritzy areas, not because the students themselves come from relatively well-off families (although some former students, like Kylie Minogue, have gone on to considerable financial success).

What this tells us is that not all households within a cluster of contiguous suburbs earn the average income – there’s considerable variability even though the suburbs might, on average, be quite affluent.

To throw further light on this issue, I looked at the incomes of families in Ivanhoe East at the 2006 Census to try and get a handle on the degree of variability in income within a small geographical area. Ivanhoe East is around the same distance from the CBD as Camberwell and has 984 families. It has about six times as many dwellings as a Census Collector’s District (Camberwell has 5,011 families).

Like Camberwell, Ivanhoe East seems a homogeneous middle class area with no obvious “good” and “bad” neighbourhoods – houses on the river or on golf courses are worth more but all the houses look substantial. This is a small but apparently affluent neighbourhood with a couple of private schools nearby – Ivanhoe Grammar, Ivanhoe Girls Grammar and Alphington Grammar. About two thirds of families in East Ivanhoe have children.

27% of families in Ivanhoe East earn more than $3,000 per week, but 46% earn less than $2,000 p.w. and 16% earn less than $1,000 p.w. I don’t think $20,000 per year in school fees for each child would be comfortable for most households earning less than $2,000 p.w., much less those earning below $1,000 p.w.

What this suggests is that caution is needed in formulating policy on the assumption that the average defines the nature of an area or region. For example, this story implies that the inner city is inhabited only by wealthy residents (who all use public transport!). While Fitzroy (say) has a much higher proportion of residents who work in Professional and Managerial occupations than the national average (56% vs 33%), the remainder of the workforce are nevertheless employed in more modest occupations.

I also want to touch quickly on a related matter. As a postscript to my earlier post on My School, I see that the Financial Review quoted the Chairman of the Australian Curriculum, Assessment and Reporting Authority (ACARA), Barry McGaw, as saying that ICSEA is a robust measure for more than 90% of schools and where it is not, it has been corrected.

Some schools that are "statistically similar" to Camberwell High

I duly note that Camberwell High School and Melbourne Grammar are now no longer listed as comparable schools on the ICSEA Index.

However Carey Baptist Grammar School, whose fees for Australian residents are $19,864 p.a. for years 8-10, is listed as comparable socioeconomically with Camberwell High.  So also are Lauriston Armadale ($21,220 p.a.); Methodist Ladies College Kew ($19,085 p.a.) and Sydney Grammar School ($24,318 p.a.).

There are also a number of other ‘top flight’ private schools listed as comparable, including Melbourne Grammar (Wadhurst), Sydney Church of England Girls Grammar School, Presbyterian Ladies College Peppermint Grove and Trinity Grammar Kew (these latter schools all choose not to publish their fees).

Also included in the list of comparable schools on My School are three NSW high schools – Cherrybrook Technology High School, Pennant Hills High School and Turramurra High School.

ACARA either needs to really get on top of the problems with ICSEA or remove it (it’s not the main game anyway). Direct data on the socioeconomic status of the parents of students would of course be much better but I can see that would be difficult to gather. An alternative could be to sample private and public school parents in order to derive a statistical weighting that could be used to obviate the sorts of anomalies noted above. That should enable fairer comparisons.