The Finnish education system is a pretty good one. Does the job of getting almost all to the jumping off point for further study. However, rather too many people then start to project their own prejudices onto it - and the thing is it just isn't as some would have it. This is important as we discuss that subject of grammar schools ourselves.
For example, this in The Guardian:
The success of Finland’s comprehensive school system is a story now well-told. At the turn of the century, much to the surprise of the Finns, let alone the rest of the world, it emerged as a global leader in education. Pisa tests revealed Finnish pupils produced some of the world’s highest scores in maths, science and reading. In the three subsequent reports, the last in 2012, the country’s performance dropped slightly but it remains the highest-ranked in Europe.
Its success came under a system built resolutely against the grain of prevailing education fashions adopted by developed countries, including the UK, in the 1980s and 90s. In Finland, children do not start formal academic learning until seven. Driven by a commitment to equality (on both moral and economic grounds), it outlaws school selection, formal examinations (until the age of 18) and streaming by ability. Competition, choice, privatisation and league tables do not exist. “Teaching to the test” is an alien concept. Grammar schools, the UK government’s current obsession, were abolished decades ago. Free school meals, tentatively endorsed for younger pupils only in the UK, are universally provided.
The error in there is that it's not actually a comprehensive system. Here's the actual structure of the system. Or a written description.
Upper secondary education begins at 16 or 17 and lasts three to four years (roughly corresponding to the last two years of American high school plus what in the USA would be a two-year Community or Junior College). It is not compulsory. Finnish upper secondary students may choose whether to undergo occupational training to develop vocational competence and/or to prepare them for a polytechnic institute or to enter an academic upper school focusing on preparation for university studies and post-graduate professional degrees in fields such as law, medicine, science, education, and the humanities. Admissions to academic upper schools are based on GPA, and in some cases academic tests and interviews. For example, during the year 2007, 51% of the age group were enrolled in the academic upper school.
It is comprehensive up to the age of 16, just as our primary schools are comprehensive, and then there's a very rigid division into the academic and vocational streams. To the extent that the two only meet again, and this is very much a might meet again, at the PhD level.
It's entirely possible to argue that perhaps 11 isn't the right age at which to decide upon the split. Or that 16 is or any other combination of such ages. But we can't go around pointing to what is said to be the world's best system and argue that it proves that we should not split - not when that "world's best system" does indeed split.
Effectively that world's best system splits at O Levels when we measure it against the English system. And after that split there's a vocational route up and through technical colleges and something very like City and Guilds, an academic route through A Levels and universities.
You know, that system we've spent the last few decades abolishing in the name of better education?