Also: the stuff measured by PISA (Math, sciences & reading) is only around 50% of the national curricula. The rest are about foreign languages, arts & excercise, religion, philosphy, history etc... There are more art, craft & music classes than say, mathematics. While wasting less time teaching and learning in classroom than most (http://blog.coreknowledge.org/2010/04/09/less-school-higher-...). If I were to engineer a PISA-breaking education system, I would probably not approach it like that.
(The curricula (.pdf): http://www.minedu.fi/export/sites/default/OPM/Koulutus/yleis...)