Changes in the demographic profiles of geographical areas between census years may invalidate many comparisons of so-called “like schools” on the My School website.
The measure of school socio-economic status used to construct “like school” comparisons is already out of date by nearly four years as it is based on 2006 Census data. It will become even more out of date before new Census data is available in 2013 or 2014.
Since the last Census, major changes have occurred that have potential to cause the actual SES of many schools to differ from their rating according to the Index of Community Socio-Educational Advantage (ICSEA). For example, the global financial crisis has increased unemployment in Australia and the pattern of unemployment varies across different regions.
This may mean that the actual SES of some schools in these regions is now significantly below their measured SES according to the 2006 Census data and below that of schools considered by My School to be statistically similar.
Ongoing changes in the demographic profiles of suburbs between Census dates may also change the actual SES of schools in some areas and invalidate the ‘like school’ comparisons determined by ISCEA values. A classic example from the past was the large scale movement of higher income families into inner suburban areas to replace low SES families. This is still going on in some cities.
Such changes have the potential to cause the actual SES composition of some inner city schools to be significantly different from that indicated by their ISCEA value.
Social change is an ongoing phenomenon. Census data are collected every five years and it usually takes 2 or 3 years to construct the new SES index values. The next Census is in 2011 and new data will not become available for at least two years after that.
This means that the My School measure of SES could become outdated by 7 or 8 years. Significant social change affecting school SES can occur within this period and invalidate many comparisons of the results of so-called “like schools”.
Trevor Cobbold