Foreign Correspondent: Education Gangnam Style

Education has powered South Korea's stunning economic success. A country once shackled by mass illiteracy now tops academic league tables. But as North Asia Correspondent Matthew Carney reports, its stressed out students also rank as the unhappiest in the developed world.

It's 11pm and across South Korea the cram schools are finally set to close. For millions of bleary-eyed teenagers it's the welcome end of a 15 hour school day.

Next morning in the first lesson, exhausted students fall asleep at their desks. It's just another day in a society that prizes academic achievement above all else, where young lives are charted by success or failure in getting the marks to make it into a top university.

At the heart of this system is a $20 billion private industry dominated by cram schools, or hagwons, that constantly test and retest students.

Feeding off the system are entrepreneurs like Cha Gil-yong, a celebrity teacher whose schtick is to don wigs and wacky costumes in his online lectures. He rakes in $8 million a year. At any one time 300,000 students are logged into his website.