Of 6.48 million schoolkids in Korea, 1.05 million or 16.3 percent need special attention for signs of depression or a violent disposition, a survey suggests. Some 220,000 students or 4.5 percent are considered at risk and require a mental evaluation and treatment.

The Ministry of Education, Science and Technology conducted two behavioral and mental health checkups on elementary, middle and high school students last year.

The problem is that the numbers are increasing. The proportion of children needing special attention rose from 12.8 percent in 2010 to 16.3 percent last year, and the proportion of at-risk kids from 2.6 percent to 4.5 percent.

Middle-schoolers took up the highest proportion in the at-risk group with 7.1 percent, followed by high school students (5.4 percent) and elementary schoolchildren (2.4 percent).

The main reason for the increase, however, is that the proportion of schoolchildren who participated in the tests reached 97 percent for the first time last year, compared to around 70 percent in previous years.

Experts said many children from dysfunctional families did not participate in the previous tests.

Another reason is that puberty is coming faster. "Adolescents around the age of 14 are very independent and impulsive but have immature judgment", said Koh Yun-joo of the Korea Institute for Children's Social Development. "Although the development rate of their bodies and minds is little different from the past, stress from studying increases and the media and video games have expanded in a fast-changing society, so puberty comes too fast and too intensely".