YOUNGSTERS are clamouring to be heard and a two-hour live programme on RTHK Radio 3 is fast replacing Sesame Street as top-rated day-time entertainment. Kids Hour , presented by the mad-cap duo Matthew Scarff and Larry Ottaway, is a mixture of competitions, feature stories and music aimed at children and teenagers. Initiated during the summer holidays last year, the programme has achieved something close to cult status among youngsters who tune in five days a week hoping to get their chance at stardom on the airwaves. ''We just felt that there wasn't a specific time-slot for kids,'' said Colleen Joynt, producer of Kids Hour . ''There was this untapped market whereby kids could be encouraged to phone in and take part.'' Response was enthusiastic, with the programme now attracting audiences ranging from six to 16 years old who are keen to contribute their ideas. Larry Ottaway, a veteran personality on RTHK, met co-presenter cum reporter Matthew Scarff when the latter did a review of the INXS concert on the programme. The chemistry between them gave Kids Hour the spontaneous energy it needed as a live broadcast. ''It's totally chaotic, really wacky when we co-present,'' said Ottaway of the non-scripted show. He said the impromptu chit-chat works despite their different personalities and interest. ''I think it's great that kids are so natural on the air . . . most of those who call up have great personalities and we always have a good laugh,'' said Scarff. Apart from competitions like Manic Maggots and Beat the Clock, the programme also features computer games and book reviews that promote creativity among youths. Like all radio shows, Kids Hour has its devoted fans. Charles, Nicole and Alison D'Souza are very fond of the programme, especially the quizzes and competitions. ''Some of the competitions are quite hard, and I like the features they do like the time they had a stuntman from Archaos come in and we could phone in with questions for him,'' said 15-year-old Charles, who reviewed a horror book for the book review segment. His sister Alison, 10, would like more jazz on the programme, while 12-year-old Nicole would like live sports telecasts and film reviews. Warren and Sarah Farrington are avid fans of the competitions, with seven-year-old Sarah picking up two computers in a story-writing competition last year. ''I'd like to have more requests for songs, but I enjoy all the quizzes and competitions,'' said 10-year-old Warren, a computer buff. Kids Hour is set to reach out to an even larger audience as it gains momentum with Chinese-speaking listeners. ''I think the programme is beneficial for those who don't speak English as their first language,'' said Joynt.