According to the data compiled by Statistics Korea, 80 percent of the country's elementary school students received supplementary education services in Korean, English, mathematics, sports and arts curricula between 2007 and 2016.
The rate has been on a decline since 2007, when the comparable figure was 88.8 percent.
In 2016, 63.8 percent of the middle school students were involved in private education, down from 74.6 percent in 2007, with the number falling to 52.4 percent from 55 percent among high school students over the cited period, the data showed.
The monthly spending on private education by elementary school students reached 241,000 won (US$228) over the cited period, with figures being 275,000 won and 262,000 won for those in middle school and for high school, respectively, the latest data showed.
South Korean parents are known for their enthusiasm about education, with private education spending staying significantly high, though its growth has been slowing in recent years.
Monthly expenditures on private education here reached an all-time high last year amid a steady drop in the number of students.
Average spending on private education per month stood at 271,000 won per child in 2017, up 5.9 percent, or 15,000 won, from a year earlier, earlier data showed.
It marked the largest monthly total since 2007, when the government started to compile such data.