Ironic that the main reason people keep writing about how great the schools are in Finland is their performance on a standardized test (PISA).
No we don't. When the first splendid PISA results were published in 2003 and 2006, the common theme in Finnish media was to wonder what is wrong with the methodology of those tests, because Finnish school system cannot be world class, no way.
It took years and years of foreign media publicity and foreign interest, before we in Finland slowly started to believe that maybe our schools are, maybe, kind of good, because the rest of the world seems to believe so. And the rest of the world cannot probably be wrong.