Singapore heads the table, followed by Hong Kong, with Ghana at the bottom.

The UK is in 20th place, among higher achieving European countries, with the US in 28th.

The OECD economic think tank says the comparisons - based on test scores in 76 countries - show the link between education and economic growth.

"This is the first time we have a truly global scale of the quality of education," said the OECD's education director, Andreas Schleicher.

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"The idea is to give more countries, rich and poor, access to comparing themselves against the world's education leaders, to discover their relative strengths and weaknesses, and to see what the long-term economic gains from improved quality in schooling could be for them," he said.

The top performer, Singapore, had high levels of illiteracy into the 1960s, said Mr Schleicher, showing how much progress could be made.

In the UK, the study shows about one in five youngsters leave school without reaching a basic level of education - and the OECD says that reducing this number and improving skills could add trillions of dollars to the UK economy.

"I think it's partly a mindset, an expectation. There are plenty of examples of schools that have raised the bar dramatically," said education minister Lord Nash.

The analysis, based on test scores in maths and science, is a much wider global map of education standards than the OECD's Pisa tests, which focus on more affluent industrialised countries.

This latest league table, ranking more than a third of the world's nations, shows how countries such as Iran, South Africa, Peru and Thailand would appear on an international scale.

It shows once again the poor performance of the United States, slipping behind successful European countries and being overtaken by Vietnam. It also highlights the decline of Sweden, with the OECD warning last week that it had serious problems in its education system.

Figures mapped above show estimated growth in GDP over the lifetime of pupils. The figures assume that all pupils are enrolled in schools and that they achieve at least basic skills.

"Poor education policies and practices leave many countries in what amounts to a permanent state of economic recession," says the report.

Millennium targets

Improving education would produce "long-term economic gains that are going to be phenomenal", says Mr Schleicher.

If Ghana, the lowest ranked country, achieved basic skills for all its 15-year-olds, the report says that it would expand its current GDP by 38 times, over the lifetime of today's youngsters.

The report will provide evidence for next week's World Education Forum of how achieving education targets can deliver economic gains.

The milestone conference, under the auspices of the United Nations, will mark 15 years since the setting of education targets by world leaders.

These millennium targets for education, such as providing all children with a primary education, have not been fully achieved.

But the World Education Forum will set another round of global targets for the next 15 years.

Source: BBC