More than 90 percent of schoolchildren in South Korea own a mobile phone and they start using them at an average age of 10 years and fours months, according to a survey published Friday. The study, conducted by a local politician and Dankook University's medical school, polled 6,052 elementary, middle and high school students. It found that some 96 percent of middle and high school students and 83 percent of elementary students owned a mobile and the monthly average phone bill was 27,290 won ($23). Asked about the ban on mobile phone use in school, about 48 percent of elementary school students agreed while more than 70 percent of middle and high school students opposed the policy. Teachers strongly support the ban, saying it gives them greater control over children during classes. South Korea had about 51 million mobile phone subscribers at the end of February, more than the population of 48.6 million, with a growing number of people carrying more than one handset.