In a research brief, the OECD noted the growing number of studies pointing to the importance of learning for children aged up to five.

Australia's preschool enrolment rate improved between 2005 and 2010, the report said, but was low at 51 per cent compared with the OECD average of 79 per cent.

The best-performing countries, such as France, Germany, Japan, New Zealand, Spain, Norway and the UK, had enrolment rates of more than 95 per cent.

Trevor Cobbold, the national convener of Save Our Schools, said the figures were due to low enrolment and spending in NSW and Queensland.

''The report on government services published by the Productivity Commission shows that 55 per cent of children in the year before full-time school in NSW were enrolled in preschool in 2011-12,'' Mr Cobbold said.

''The figure for Queensland was 39 per cent. This compares with about 100 per cent in Victoria, WA and Tasmania, 92 per cent in South Australia, 88 per cent in the ACT and 86 per cent in the NT.''

The research also found Australia spent less than 0.1 per cent of gross domestic product on early childhood education, based on 2009 figures.

Countries including Denmark, Iceland, Israel and Spain spent 0.8 per cent of GDP, well above the OECD average of 0.5 per cent.

''Without sufficient public spending, there is a greater risk that access to early childhood education and care programs will be restricted to affluent families and the quality of the programs will vary,'' the research warned.

Early Childhood Australia released a report in February saying children who attend childcare centres with more and better-qualified educators start school with superior social, language, literacy and numeracy skills.

The federal government has introduced new childcare regulations that require higher staff-to-children ratios and better educational qualifications. But childcare staff remain among the lowest paid workers in the country, typically earning less than $20 an hour.

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