Threadworms are transmitted by human to human and dog to human contact. Better to be safe than sorry and it’s advised that everyone deworms themselves every three months as a preventative measure. I’d say the school is practicing very safe hygiene!

I looked threadworms up. Apparently, thoroughly scrubbing yourself down during your daily ablutions is sufficient to prevent the spread of the parasite, as is washing your hands after you use the bathroom or pet an animal. "Regular deworming" is not good hygenic practice. "Regular deworming" is what you do after someone has <i>utterly failed </i>at good hygenic practice.

Good luck with getting an entire school full of kids (and many teachers!) to thoroughly scrub themselves and their hands regularly. Worms spread. Fact. Deal with it.