Both yours and theirs can be true. Perhaps preschoolers in Asia have better parental modeling of proper mask wearing, having been a fairly widespread practice in some areas since the first SARS. Perhaps there's a difference in how careful the teachers were to make adjustments when someone's slipped.

While you see most westerners wearing their mask below their nose, the kids follow suit.

In Taiwan since September last year, enrolled my daughter in school, every kid in her class wears a mask, they get temp check before being allowed into school, teachers help the kids with the masks. So far her class has had 1 kid who got covid, stopped coming to school, got better, that's it. No outbreak.

So good mask wearing starts with the parents. In asia we take covid seriously, other than westerners you rarely ever see locals not wearing masks correctly.

Pretty much all masks are surgical 3ply now, at the start of covid it was quite hit and miss, alot of 'surgical' were not 3ply.