(2013 version) Why does Finnish give better PISA results?

Taksin Nuoret:

Ever since December 2001, when the results of the first PISA survey were made public, the Finnish educational system has received a lot of international attention. Foreign delegations are flocking to Finland, in the hope of discovering Finland’s secrets. Finland is also trying to take advantage of its PISA success by exporting its knowledge in education [1]; this strategy is supported by talks given in international events by representatives of the Finnish Ministry of Education and Culture [2].
The explanation widely accepted is that the Finnish educational system is better. For example, the following aspects have been pointed out:
Schools routinely provide tutoring for weak students.
Each school has a social worker (“koulukuraattori”).
Substitute teachers are often provided when the teacher is ill.
Teachers are seldom on strike.
The methods used for teaching mother tongue are solid. Finnish first graders learn to read first by learning letters, then syllables, then words, then sentences. For example, throughout grade 1 (and most of grade 2), words are often printed with syllables separated by hyphens [3]. Adventurous approaches (such as starting with words or sentences as wholes) are not used.
Schools have more autonomy than in many countries. For example, schools can dismiss teachers if they are not satisfied with their work.
The profession of teacher is better recognized than in many countries.
Transition from low to high grades of the Finnish curriculum is smoother than in many countries.
Finnish students have a free canteen at their disposal.
Explanations not related to the educational system have also been proposed, including:
The Finnish society is homogeneous. The number of foreigners is lower than in most OECD countries (3.6% at the end of 2012 [4]), which makes the teachers’ job easier.
Finnish spelling is regular, thus easing Finnish students’ task.
Foreign TV programs are subtitled, instead of dubbed as in many OECD countries, thus easing acquisition of foreign languages.