By the numbers - Pisa rankings
Growing numbers of poorer countries are taking part in the world's most influential education rankings despite facing more challenging circumstances.
The Programme for International Student Assessment (Pisa), set up by the Organisation for Economic Cooperation and Development (OECD), evaluates the school systems of 34 member countries. But the involvement of other countries has grown, with more than 40 "partner" countries or regions taking part in 2009 (the last assessment for which figures are available). Pisa is carried out every three years to test the reading, mathematics and science abilities of 15-year-olds.
However, changes need to be made to make the tests more relevant and useful to lower-income countries, according to an OECD working paper. One of the biggest barriers for developing countries is the fear that they will appear at the bottom of the rankings, according to the paper. Classification on the basis of economic and social development, rather than OECD membership, is a more useful approach for those countries, it says.
Other aspects that need addressing include the fact that many 15-year-olds in poorer nations are not in school. Low- and middle-income countries may also have issues relating to the achievement of minorities, whereas in richer countries the achievements of immigrant children will be of particular interest, the paper says. The OECD is working to tackle these and other barriers.
Mean reading scores of partner countries, 2009
472 - High-income countries
420 - Upper-middle-income countries
372 - Lower-middle-income countries
314 - Kyrgyzstan (only low-income country).