I don't think they learn Mandarin to the extent they learn EnglishMuch the same as Phils, wifes kids started at that age, But they don't do Mandarin although I think Mandarin is good to learn especially if you live in Asia.
I know, even in the village school, they give proper English class
Because I have helped some of the kids when there
My stepson speaks and write English rather well
He really improved in high school