The Australian Early Development Census is a three-yearly government study which tracks early childhood development based on data from children in the first year of full-time school.
The five "domains" covered are: physical health and wellbeing; social competence; emotional maturity; language and cognitive skills; and communication skills and general knowledge.
The latest report showed most Australian children were "developmentally on track" for each of the five domains.
But between 2018 and 2021 the percentage of children on track in five domains fell for the first time since 2009 - from 55.4 per cent in 2018 to 54.8 per cent in 2021.
The 2021 data also shows a small but significant increase in the percentage of children who were "developmentally vulnerable".
The "social competence" domain was the only domain where the level of vulnerability decreased - from 9.8 per cent in 2018 to 9.6 per cent in 2021.
Education Minister Stuart Robert said children, families and schools had shown enormous resilience and flexibility in unprecedented times.
He said the census would give governments the data they needed to make informed decisions about where to target programs, especially in vulnerable and disadvantaged communities.
Meanwhile, Australian COVID-19 infections are continuing to surge due to a sub-variant of the Omicron strain, as health authorities warn cases will not peak until mid-April.
Figures reported to the Australian Health Protection Principal Committee noted the number of daily COVID-19 cases increased by more than 76 per cent between March 11 and March 23, while hospitalisations from the virus rose by almost 25 per cent in the same time period.
However, in the two-week period, deaths were down by seven per cent, and the number of patients in ICU had decreased by five per cent nationally.
LATEST 24-HOUR COVID-19 DATA FROM ACROSS AUSTRALIA:
NSW: 25,495 cases, two deaths, 1345 in hospital, 43 in ICU
Victoria: 10,424 cases, six deaths, 310 in hospital, 12 in ICU
Tasmania: 2108 cases, no deaths, 30 in hospital, none in ICU
ACT: 1014 cases, one death, 46 in hospital, two in ICU
