South Korean children are the least happy in study among developed countries, the government said on Tuesday, citing the stress of the country's educational pressure cooker.

South Korea ranked at the bottom among 30 countries in terms of children's satisfaction with their lives, the country's health ministry said, followed by Romania and Poland.

"The most relevant factor to the children's life satisfaction is academic stress, followed by school violence, internet addiction, negligence and cyber violence," the ministry said of its survey of more than 4,000 households with children younger than 18.

World Bank chief Jim Yong Kim, himself born in South Korea, said the educational system put a heavy burden on children, with its focus on competition and long hours of work.

South Korea's survey results were measured against those of 27 members of the Organisation for Economic Cooperation and Development (OECD) grouping of 34 wealthy countries, plus Romania, Latvia and Lithuania.

The survey, the first such exercise by the South Korean government, comes as around 600,000 students gear up for the annual college entrance exam, with places in prestigious schools and a pathway to a secure job at a top corporation on the line.

When the test is held on Nov 13, the country's stock market will open an hour later, office openings will be delayed to ensure students don't get stuck in traffic, and the central bank will delay its interest rate-setting meeting by one hour.

Domestic air traffic will be curtailed during the listening comprehension portion of the exam.

More than half of children aged between 15 and 19 who are suicidal give "academic performance and college entrance" as a reason, according to National Statistics Korea.

South Korean parents are well-known for marching their children off to cram schools until late in the evening, and beginning English tutoring in kindergarten.

South Korea also made a poor showing in the survey's child deprivation index, which includes child poverty as well as time for hobbies and school or club activities. It came in last, after Hungary and Portugal.

World Bank Group President Jim Yong Kim, who was born in Seoul and moved to the United States at age five, said that South Korea's education system exacted a heavy cost.

"Students endure a substantial psychological burden from competition and long hours of work," he said during a visit to Seoul on Tuesday.