Actually it is a brilliant idea. Having kids in who were brought up in Sweden I know a lot about their system. They do not start till six, and they spend the first year with numbers and the alphabet, sing nursery rhymes and generally learn slowly. They also start learning English at six. Usually just nursery rhymes but that is it. Nothing major. By the time they are 11 they have caught up and are at the same level as kids here. That plus they all generally have good English skills. My Swedish is crap, mainly because learning a new language with amnesia is very tough. Though that was not a problem as pretty much everyone below 40 is bilingual.

So I have seen it work. That plus they can all read unlike here is a major plus.

I think I've saw some of those 'documentaries'

Yes I think I know what documentaries you are thinking of. They do help with your learning of Swedish swear words. Though having kids in Sweden means that you do not need them to learn such words. The oldest daughter has moved nearby to study and my ability to swear in Swedish came right back.