The rankings combine international test results and data such as graduation rates between 2006 and 2010. (bbc.co.uk)
Consider analyses of international test results. (ctacusa.com)
Lithuania Policy Research Capacity Project In this project (2001 - 2003), 3 policy research studies were carried: 1) How do school and student factors explain variation in a national standardized test; 2) Why is the national test result not correlated with international test results? (gse.harvard.edu)