The secret of Finland's stellar schools is Finns[1], combines with an immigration policy that borders on xenophobia. Why do Finnish students score better than Swedish students?
This blog [1] claims, and the reference 11 therein (or directly [2]) shows, that the Swedish-speaking Finns score lower than Finnish-speaking Finns. It pretty much cannot be explained by socio-economic status, as Swedish-speaking Finns have higher socio-economic status than Finnish-speaking Finns. So the blog conjectures that it might be related to the languages.
Finland had below-average schools until the 1970s, then they got serious about reforming them, and now they're on top. So none of this bullshit applies.
[1] http://www.vdare.com/articles/pisa-scores-show-demography-is...