notably Eric Hanushek, Ludger Wößmann, Heiner Rindermann, and Stephen J. Ceci, with material for books and articles about the relationship between student achievement and economic development, democratization, and health; as well as the roles of such single educational factors as high-stakes exams, the presence or absence of private schools and the effects and timing of ability tracking. Comments on accuracy David Spiegelhalter of Cambridge wrote: "Pisa does present the uncertainty in the scores and ranks - for example the United Kingdom rank in the 65 countries is said to be between 23 and 31. It's unwise for countries to base education policy on their Pisa results, as Germany, Norway and Denmark did after doing badly in 2001." According to a Forbes opinion article, some countries such as China, Hong Kong, Macau, and Argentina select PISA samples from only the best-educated areas or from their top-performing students, slanting the results. According to an open letter to Andreas Schleicher, director of PISA, various academics and educators argued that "OECD and Pisa tests are damaging education worldwide". According to O Estado de São Paulo, Brazil shows a great disparity when classifying the results between public and private schools, where public schools would rank worse than Peru, while private schools would rank better than Finland. See also Gender gaps in mathematics and reading in PISA 2009 Progress in International Reading Literacy Study (PIRLS) Teaching And Learning International Survey (TALIS) Trends in International Mathematics and Science Study (TIMSS) Explanatory notes References External links OECD/PISA website OECD (1999): Measuring Student Knowledge and Skills: A New Framework for Assessment. Paris: OECD, OECD (2014): PISA 2012 results: Creative problem solving: Students' skills in tackling real-life problems (Volume V) OECD's Education GPS: Interactive data from PISA 2015 PISA Data Explorer Gunda Tire: "Estonians believe in education, and this belief has been essential for centuries"—Interview of Gunda Tire, OECD PISA National Project Manager, for Caucasian Journal 2012 in education Student assessment and evaluation Educational research International educational organizations International rankings Lists of countries OECD Organizations based in Paris Organizations established in 1997 Statistical service organizations