To give you some idea of how important this exam is, consider the following facts.
- During the listening test, airoplanes are not allowed to take off or land.
- Offices and the stock market open an hour later than usual to clear traffic for the test takers.
- Some parents anxiously wait outside the school for the entire 9 hour exam.
- Police escort late students and deliver forgotten schoolbags to school.
- The Korean Electric power company places 4000 employees on standby in case of an emergency.
The other year levels get the day off from school, but still go to school and wait out the front to offer their support and encouragement to the senior students sitting the exam.
To prepare for the exam students will study 7 days a week. Many will get up at 6:30am, go to school, then to a hagwan (cram school), and then to a private (quiet) study room before getting home at 2am.
Students start thinking about and preparing for the exam in middle school. As they progress through middle school and high school their study hours steadily increase until they reach ultimate levels of craziness in their final two years of high school. They focus all their energy and time on studying for this exam. In their final years of high school, they give up playing sport, watching movies, playing games and spending time with their family in order to study for the exam.
Many students view the intensive study to successfully complete the exam as a right of passage. In Australia we had a national test called the QCS. It is what determined what you could study and what university you could attend. There was a lot of pressure to do well in the QCS test, but nothing like this. We were always told "Do your best. Doing well will make your life easier, but it is not the be all end all of your life. There are other paths to university." There is no sense of that in Korea. People believe that what you score in Sooneung will set the tone for the rest of your life. Given that belief, it is strange that students report feeling hopeless and empty after completing the exam. What is the point of the exam?
There is an excellent (short) documentary on Sooneung <here>.
EDIT: Check out this nutty question on the English portion of the exam.