THE common sight of schoolchildren bent in half under the weight of overloaded school bags has provoked public outcry for years, and recently the matter has come up for debate before the Legislative Council and discussion in the media. Last week Radio Television Hongkong (RTHK) brought up the topic in the new educational programme ''Children News Magazine - Mini-forum''. Weighing the school bag issue were Mr Cheung Man-kwong, chairman of the Hongkong Professional Teachers' Union, and showbiz personalities Karen Mok, Julian Cheung, Hung Yan and Junior Anderson. Educationist and legislative councillor Mr Cheung said several of his colleagues had voiced concern about the problem during recent Legco meetings. ''We believe students are at great risk carrying heavy school bags,'' Mr Cheung said. ''Besides lots of thick textbooks, the bags also contain metal pencil boxes and water bottles, all adding to the weight.'' ''We hope the Education Department will discuss the matter of heavy textbooks with the publishers. The answer is to print a textbook in several volumes, using thinner sheets of paper.'' Teachers for their part could help by telling students exactly what books were needed the next day, Mr Cheung said. ''Children are often scared they'll be punished for not bringing the correct books to class, so they play safe and take all the books to school every day,'' Mr Cheung said. He added that it would be a help to students if they were provided with ''tool books'' like dictionaries at school. Cloth pencil cases could replace metal ones and children could use school drinking water facilities instead of carrying water bottles, he pointed out. Pop singer Julian Cheung stressed the potential dangers of physical injury caused by heavy school bags, while Hung Yan suggested that students avoid carrying ''unnecessary things'' like pop star magazines and picture albums in their bags. Also taking part in the discussion were four students - Wong Bo-long, Tse Ying-dip, Mary Chan and Arthur Chan. The ''Children News Magazine'' is a forum for current affairs aimed for children, with children present to give their point of view. Just before last week's mini-forum got underway, Mr Wong Chi-keung, Controller of News and Current Affairs (TV) at RTHK, explained that lately there had been a demand for current affairs programmes with children taking part. RTHK's response was the new TV series, broadcast on the ATV Home Channel every Sunday at 7 pm. Each episode focuses on a new topic closely related to the world of students and children. The programme includes a a cover story, a feature, a news roundup, and reviews of films and television shows.