It’s been widely noticed that Finnish school system definitely has some good properties. You can find an official description for example from here but in this series I take into consideration some features that may not come into attention internationally that often.
Literacy rate in Finland is very high. Wikipedia uses the Unesco 2015 list that doesn’t have Finland in it, other sources claim it to be even 100% . This is a rounded number, but we can anyway say that the literacy rate has been very high for decades.
It’s said that Finnish language is very difficult, it’s conjugations are numerous. That’s true, it’s hard for foreigners to master these perfectly. But, when you can speak Finnish, it’s ridiculously easy to read. All letters have one-to-one pronunciation. Exceptions are very rare and minor. Here is a major advantage to English speaking kids, who almost have to learn a new language, written English after learning spoken English.
There are not many languages related to Finnish. If we are looking for close relatives, there is only one that goes with a country so that we can see its Pisa results: Estonian language. And it happens that Estonia is very high in Pisa rankings, in 2018 it outperformed Finland.
Wait, what some old Disney character has to do with this? Donald Duck (Aku Ankka in Finnish) is an institution when talking about magazines in Finland. It’s by readers count the most popular magazine if free  magazines are left out. Reader count is a bit bigger than the number of under 20 year olds  , because some adults read it, too.
You may know that it’s common to dub TV shows to other languages? In Finland, programs that are intended for adults are never dubbed. Programs for the teenage audience very rarely are dubbed, either. Dubbing is for kids, and self-respecting 10+ years old can watch television with subtitles. If you are a school kid in Finland and want to see original (or new) Star Wars movies for example, you have to be able to read subtitles fast enough to keep in track. That’s one thing that adds motivation.
The last random fact
Finland has been under Swedish reign for centuries and Swedish language has been the language in society’s top layers for long, too. One of the first novels written purely in Finnish was Aleksis Kivi’s Seven Brothers. It’s a growth story of seven orphan brothers. One part of the novel describes how it’s very difficult for these boys to learn to read and their teacher is harsh on them. But, they bang their heads on the wall (metaphorically) until they figure it out and that will give them church permission to marry. That is one of the stories Finnish school children have to get familiar with.
To sum it up, in Finland, there is a very strong assumption that every proper citizen can read. It’s the matter of discussion whether reading and understanding read text has gone downhill due to digitalization.
Random numeric facts about the author:
5 Number of years she’s been teaching in Finnish public school (other than public schools are rare exceptions.)
8 The author’s grade in English language (scale 4-10) in Finnish school. That should explain funny grammar/word choices in text.
20 Number of years the author has been a subscriber to Aku Ankka magazine.
See also: Finland’s education system explained