The population of children and underage students in the capital of Seoul has nearly halved over the past 20 years amid the country's low birth rate, city data showed Thursday.

The total population of Seoul residents aged 17 or lower amounted to 1.59 million last year, a 45.6 percent dive from 2.92 million registered in 1994, according to the data.

The underage group accounted for 27.1 percent of the capital's total population in 1994, but the ratio dropped to 20.9 percent in 2004 before tumbling further to 15.7 percent in 2014 when the total population reached 10.1 million.

The downtrend brought the number of Seoul's elementary students down to 457,517 last year, nearly halving from 20 years ago. It was the lowest number of elementary school-level children since the data was first compiled in 1965.

The number of middle school students was also cut in half to 286,826 last year, the first figure coming under the 300,000-threshold since 1971, the data showed.

The shrinking underage population also led to smaller school classrooms, with an average of 30.2 students sitting together in one classroom. It was a sharp fall from the average of 51.9 in 1994.

The data came as South Korea's fertility rate has been stalling between 1.2 to 1.3 children per woman in recent years. It is the lowest level among the member countries of the Organization for Economic Cooperation and Development.

Meanwhile, the data also showed that 80.6 percent of Seoul's middle and high schoolers were under stress for various reasons ranging from school records, family matters, relations with friends as well as looks.

Only one of every 100 students sought teachers for stress consultation while the majority of them chose to consult their friends, according to the data. (Yonhap)