Comparing community results

Comparing community results

Every three years, the AEDC collects data on all children in their first year of full-time school in Australia, this involved over 308,000 children in 2018. AEDC data is collected for individual children and reported at a group level (national, state/territory and community).

The results include the number and proportion of children developmentally vulnerable, as well as demographic information about the children surveyed. To understand the AEDC results it is important to understand how results are calculated and interpret their meaning.

How the AEDC is calculated: scores and percentiles

A key feature of the AEDC is that it enables the tracking of Australian children’s development over time. The first data collection in 2009 acts as a baseline measurement for future reference. This means the national ‘cut-offs’ established in 2009 will remain the same for all future data collections.

Teachers use an early development instrument which contains approximately 100 questions about children in their class, covering five areas (domains) of early childhood development. Responses from the questions are used to determine an overall score out of 10 for each domain.

The national cut-offs are applied to determine whether an individual domain score places a child ‘on track’, ‘at risk’ or ‘vulnerable’.

To establish the national cut-offs in 2009, all children’s domain scores were ranked from lowest to highest.

  • Children developmentally ‘on track’
    Children who score above the 25th percentile (in the top 75 per cent), determined using the cut-off points established in 2009, are classified as ‘on track’.

  • Children ‘developmentally at risk’
    Children who score between the 10th and 25th percentile, determined using the cut-off points established in 2009, are classified as ‘developmentally at risk’.

  • Children ‘developmentally vulnerable’
    Children who score below the 10th percentile (in the lowest 10 per cent), determined using the cut-off points established in 2009, are classified as ‘developmentally vulnerable’. These children demonstrate a much lower than average ability in the developmental competencies in that domain.

  • Children are considered to be at particularly high-risk developmentally if their score indicates vulnerability on one or more domains.

Key considerations for understanding AEDC results

The results show how local children are doing relative to, or compared with, other children surveyed both within their community and across Australia at one point in time. For example, a community that has a lower proportion of developmental vulnerability than the national results is doing proportionally better than the rest of Australia.

Proportion versus number

When comparing the proportion of children developmentally vulnerable between years, it is important to consider the number of children as well as proportion.

It is important to be cautious when interpreting results at the community level. When a community is small, it only takes a change in a few children to have a big impact on the proportion of children who are vulnerable.

The following table demonstrates how a slight change in the number of children developmentally vulnerable will have a bigger impact in a small community than in a large community. Community A has 200 children and Community B has 20 children. If 10 per cent of children are vulnerable in both Community A and B, this equates to 20 children in Community A but only two children in Community B. Add two more vulnerable children to each community and Community A now has 11 per cent of children with developmental vulnerability, and Community B now has 20 per cent of children with developmental vulnerability.



AEDC result (Number)

AEDC result (Proportion)

Addition of 2 vulnerable children to each community

AEDC result (Number)

AEDC result (Proportion)

Community A







Community B







Key considerations for tracking progress over time

The AEDC has now been measured nationally at four points in time (2009​, 2012, 2015 and 2018) providing the opportunity to monitor the progress of children’s development across each of the domains. For example, if children are faring better on the Physical Health and Wellbeing domain, we would expect to see fewer children with a developmentally vulnerable score. That is, we would expect less than 10 per cent of children to be developmentally vulnerable and more than 75 per cent of children on track.

Another way to monitor children’s progress is to look at a summary indicator of development, for example ‘developmentally vulnerable on one or more’, or ‘two or more' of the five domains. In 2009 the proportion of Australian children developmentally vulnerable on one or more domains was 23.6 per cent. In 2012, the proportion of children developmentally vulnerable on one or more domains was 22 per cent. This indicates an overall improvement of 1.6 percentage points in children’s development from 2009 to 2012.

To determine whether this improvement is a trend or a short-term improvement in children’s development over an extended period of time will depend on the results of future data collections.

Critical difference and statistical significance

Almost all communities will see some difference in the level of developmental vulnerability reported in 2012 compared with 2009. In some cases this will be small and in others it will be more substantial.

In interpreting the data a formula can be applied to determine if the difference in the number of vulnerable children is ‘critically different’. The critical difference is the minimum level of change required between the 2009 and 2012 data for the results to be significant. Significant in this case, means a level of certainty that the change did not occur by chance.

The critical difference formula takes into account the size of the community, the proportion of change, teacher reporting bias and the specific indicator. The Critical Difference Calculator available in the AEDC Data Explorer calculates the critical difference for a community.

Further information 

There are several resources available to help access, understand and interpret the AEDC results and what they mean for Australia and its communities. These include: