It is required to let your child go to school and home-schooling does not satisfy that requirement so is in principle illegal. There are a few ways some people

It is required to let your child go to school and home-schooling does not satisfy that requirement so is in principle illegal. There are a few ways some people do manage to get it allowed (you have to argue that your way of life / religion is fundamentally incompatible with all schools in the region) but expect quite a few visits from suspicious civil cervants and lots of arguing. That's the theory, anyway. How it was possible that these children were never checked on is still under investigation.