There might be a few children who go to kindergarten wearing diapers because they need them but most children in China are potty trained and out of diapers completely by kindergarten age.
That's the same with the USA most children in Kindergarten are out of diapers and are potty trained although some might be special needs or have bladder problems and may need to wear diapers to kindergarten or even Pull Ups.
But most kids in China and the USA are not wearing diapers even in preschool let alone Kindergarten.
Also some kids don't even wear diaper in China but instead some of the children have holes in the back of their pants to poop out of but I'm not sure about peeing.