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.

Why bother teaching your children if the world is going to end before they are adults?