The rulers adopted neo-Confucianism partly as an excuse to overthrow the old aristocracy (with whom they were fed up). Under this new system, anyone could become an aristocrat. All they had to do was pass an excruciating civil service exam, called the kwako.
In other words, the Korean political system was a meritocratic aristocracy—what an incredible oxymoron. A man from all but the very lowest classes had the right to sit for the kwako (originally instituted in the tenth century). Not only was it really hard, but it was also administered only once every three years. In a given exam year, only a hundred or so people would pass, out of thousands of applicants.
If you passed it, you were instantly given the title of yangban—you became an aristocrat. Not only that, but your whole family line was upgraded in the process. There's a catch, though. A big one. Your male heirs have to pass the kwako exam as well. If your descendents failed the exam three generations in a row, you and your family were stripped of the yangban title and went back to being nobodies. Does this not sound like something out of Grimms' fairy tales?
Ever since then, Korean students have been studying as if their lives, their family lives, and the future lives of their entire bloodline depended on it.
--Euny Hong, The Birth of Korean Cool: How One Nation is Conquering the World through Pop Culture, on extreme meritocracy