I blame two things.
One: Relative grading. Your score is lined up on a bell curve with everyone else. Grades are 1 thru 9. The center grades (4,5,6) are one standard deviation and are 50% of the total. Colleges say "screw you" if you don't have a 1, 2 or 3. 75% of Korea will fail. Sad truth. I don't care if you got a 99, fifty others in yer school got one too, so you're a grade 3.
The school year consists of sem1 midterm + sem1 finals + sem2 midterm + sem2 finals + the time between. You don't go to school to learn, you go there to be tested ._.
Two: As if One wasn't bad enough, various policies and situations along with the Korean traditional Confucianism caused zealous parents to send their children to "hakwons", private insitutions that serve to raise the bar. Nearly everyone goes to one, so math, Korean, and English are especially overheated.
Also, the fact that English is way too easy doesn't help, especially considering One.
TLDR: Relative grading plus overcompetitive "market" (of students)
The only worse place to go to high school would be Japan.
PS: Korea has the highest college graduation rate in the world, because you can't get hired at all if you only graduated high school, except for technical high schools. Also, colleges are severely ranked by name value.
Erm.. I don't know if I really answered your question. Also, sorry for those who've already read the above in other threads xD I just feel so strongly about it -_-
Another addendum: Korea is a horrid place to be a programmer. Various reasons, and even more so for females...