There is homework in Finland. I have no clue where that idea came from. The Finnish education system doesn't really match up well enough with the USA that "high school" can be compared. A Finnish student typically starts elementary school at 7, and spends 6 years in lower elementary. Then they move to upper elementary and spend 3 years there. This is where the "responsibility to learn" ends, and every school past that is voluntary. Past those 9 years, students generally choose between vocational school or a lukio, which is sort of like high school that provides general teaching. I have no clue what that 93% number means, but it is certainly not "proportion of age class that completes lukio", as less than that sign up for one.
Finnish PISA scores, and all other lower educational metrics are anomalously high when compared to similar peers worldwide. A lot of things are pointed out as reasons for this, but most of those features are also valid, for example, for other Nordic countries whose students don't perform nearly as well.
Personally, I think the difference is mostly the language. Finnish language is notoriously hard to learn, but Finnish written language is very regular and phonetic. This means that elementary school students spend a lot less time learning to read and write than students in almost any other countries. This saves much time at an early age, which can then be used to learn other useful subjects, giving Finnish students a head start on their foreign peers. A lot of us, including me, actually taught ourselves to read before school with little more than repeatedly annoying our parents by asking "What does this letter sound like?".
Then again, I might just be another idiot assigning my pet cause for a measured effect of uncertain origin.
I wonder how students fare in other countries with phonetic written languages? As I understand, Turkey is one, and their scores are not very high. Could someone describe the Turkish education system a little?