Why focus only on the lowest 25% of postcodes?

Yesterday my U of M boss, Glyn Davis, gave a speech on the difficulties in reaching the government’s target of 20% of all higher education enrolments being from a low socieonomic status background. The current definition of ‘low SES’ is living in the lowest 25% of postcodes according to the ABS index of education and occupation.

It is well established that socieconomic differences in school results are the major reason why low SES students are ‘under-represented’ at university. However, it was not until I recently analysed 2008 Victorian Year 12 results that I realised that lowest 25% seems like an inappropriately narrow target group. As the figure below shows, while students living in the lowest 10% of postcodes are clearly the weakest performers, those in the 2nd, 3rd, 4th, and 5th deciles have very similar (and not very good) school results). Very few receive ENTER scores in the 90s, and nearly half have ENTER scores below 50. While results trend upwards after the 5th decile, it is only a modest exaggeration to say that we really have the top 20% and the rest.

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