Kindergarten prowess

I wrote earlier on immersion learning in preschoolers, and how the benefit of English-themed kindergarten doesn't actually teach them English so much as it primes them to learn it in school/hagwon throughout their lives. But there's a great deal more to kindergarten here than the English. Elementary school in Korea begins in the first grade, when kids are "8" years old. That deserves a bit of clarification, so to start, school here goes from the beginning of March to the end of November. That means that on January 1st, each child's age for school purposes is considered the age they turn during the school year. So a kid whose birthday is on December 31st will start school a full year younger than a kid with a January 1st birthday. In addition, Koreans consider the gestation period to be the child's first year of life, so the day a Korean child is born is his or her first birthday. When I say they start school at 8, well, most of them are really 6.

So preschool, or kindergarten, is a private enterprise (there are general kindergartens, not just language-themed ones) that not all kids use. I wonder sometimes how far behind the kids who can't afford it are than their peers in the first grade...

But that's beside the point. I really want to compare Korean kindy kids to their American counterparts. We start kindergarten at 5 years old (effectively 3, in some cases), but my class is the oldest, the 7-year-olds. However, I have the lower-level 7s, so due to crowding in the 6yo class, I have three kids that will have another year of kindergarten before they start school. Here are the textbooks we use in class:
Spectrum Math - Grade 1 -- A book intented for first grade students. All of my students can add and subtract with ease and most of this book isn't challenging for most of them, even in English.
Super Easy Reading 1 -- I can't find much about this book, so I think it's used mostly for SLA. Very simple, but certainly very similar in structure and difficulty to some US kindergarten materials I've seen.
Master Skills Thinking Skills Grade 1 -- Again, a textbook for first graders. This one is more of a challenge from the language barrier standpoint. There were definitely some problems with sequence, but they were all because of not knowing what "last" means, not because they truly don't know. Still, most of my kids do an excellent job with this book.
Modern Curriculum Press Phonics Level K -- This one is intended for kindergartners, as to be expected.

But that's in English. In Korean, every single one of my kids can read and write (as can the age group below us) in Korean. In this, they are ahead of the majority of American kindergartners, unless there have been some dramatic changes since my siblings and I were in those grades (of my siblings, I was the only one who was reading when I entered school).

Further, I would put three of my fifteen kids into any US kindergarten right now and be completely confident that they would have no trouble with any of the material. Three more would probably be ok. And the teacher of the other 7yo class thinks all of her kids could do it.

What's the difference? Why can my Koreans read and write in Korean far better than most American kids can at the same age? I don't have an answer, but perhaps there is an expectation that kids will already be able to read, write and be proficient in basic arithmetic here when they begin school when in the US, there is a pressure for the same but perhaps not an outright expectation. Another possibility is that hangul (the Korean writing system) is easier to learn. It's certainly easier to spell, but I don't see how matching sounds to symbols is really going to be different in Korean than in English. I certainly don't think Korean children are intrinsically smarter, but perhaps the expecatations do make all the difference. The testing begins the minute they enter school, so perhaps parents make sure their kids know the basics -- even before starting kindergarten.