South Korean children are the least happy in study among developed countries, the government said 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 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.