The 2012 Australian Early Development Index, issued on Thursday, assessed 290,000 Australian five-year-olds across five measures of social competence, emotional maturity, language and cognitive skills, communication and general knowledge skills and physical health and wellbeing.

It is the largest check of childhood wellbeing of its kind - representing 96.5 per cent of children in their first year of formal full-time school, with 4900 ACT five-year-olds taking part in the study.

ACT children have improved very slightly (by 0.2 per cent) since 2009 on all measures except for physical health and wellbeing - which assesses how well they are fed and dressed for the school day - which slipped 1.2 per cent on 2009's result.

In the ACT 22 per cent of children were considered to be developmentally vulnerable across one or more measures, which is the same as the national average. A further 9.8 per cent are vulnerable on two or

more measures - slightly lower than the national average of 10.9 per cent.

The 1223 children who were assessed in Tuggeranong were the most developmentally vulnerable in the territory with 24.6 per cent assessed as vulnerable on one or more measure and 11.1 per cent vulnerable on two or more measures.

The inner north's 457 five-year-olds had the lowest risk of childhood developmental delay with just 17.7 per cent vulnerable on one or more measure and 8.4 per cent vulnerable on two or more measures. It was followed by the inner south, which had 19.5 per cent of its 269 five-year-olds vulnerable on one or more measure and 10.5 per cent vulnerable on two or more measures.

Woden had 20.2 per cent of its 406 five-year-olds assessed as vulnerable on one or more measure and 7.6 per cent vulnerable on two or more measures. Belconnen had 21.9 per cent of its 1298 five-year-olds assessed as vulnerable on one or more measure and 10 per cent vulnerable on two or more measures.

Weston Creek had 22 per cent of its 321 five-year-olds assessed as vulnerable on one or more measure and 7.9 per cent vulnerable on two or more measures. Gungahlin had 22.3 per cent of its 912 five-year-olds of children assessed as vulnerable on one or more measure and 10.2 per cent vulnerable on two or more measures.

When the statistics were broken down to individual suburbs, the suburb of Belconnen had the greatest proportion of children vulnerable on one or more measure - at 52.2 per cent - compared with Griffith, which had the lowest percentage at 5.9.

Boys tended to be developmentally vulnerable than girls on all measures as well as being more likely to be developmentally vulnerable on two or more measures.

While the majority of indigenous children were developmentally on track on all measures, they were more than twice as likely to be developmentally vulnerable than non-indigenous children. The index found 43.2 per cent of the 15,490 indigenous children assessed were vulnerable on one or more measure.

Last year, 1.6 per cent fewer five-year-olds were considered vulnerable than in 2009 - a result welcomed by federal Schools Minister Peter Garrett.

The greatest level of national improvement was in the language and cognitive development domain with 6.8 per cent of children reported as developmentally vulnerable last year, compared with 8.9 per cent in 2009.

"Australia is the only country … that collects this level of information about health, wellbeing and development of our children before they enter school,'' Mr Garrett said. ''Communities have been able to use this data to develop new programs for children and their families, and deliver extra, targeted help to children at risk.''