The biggest ever global school rankings have been published, with Asian countries in the top five places and African countries at the bottom.
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.
"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.