Education officials have defended their investigation of the case of a 13-year-old girl confined alone for five months - after teachers revealed a tape allegedly of the principal telling them to shun the pupil. No major fault was found with her treatment, the Education and Manpower Bureau told the South China Morning Post last night. Chan Sin-ting was kept isolated in a room at Po Leung Kuk Wai Yin College in Tin Wan, Aberdeen, between November and June. This week, nearly half the school's senior teachers gave the Post a tape of a staff meeting held at the school in June. On it a voice, which they say is that of principal Cecilia Yeung Mi-kuen, is heard instructing them not to help the girl. 'I hope all of you will co-operate. Don't do anything for her if she asks you to help,' the voice says. If they did not comply, there was a risk the girl would want to stay on at the school, she said. Ms Yeung yesterday denied asking them to shun the teenager. The teachers will give a copy of the tape to the education bureau. Sin-ting's case came to light in June when a letter of complaint - now revealed to have been from teachers at the school - detailing her treatment was sent to the chief executive, the secretary for education and manpower, the school's sponsoring body and a Chinese-language newspaper. Neither the girl, who is now at another school, nor her father would comment yesterday. An education bureau spokesman said it had found no major problems with the school's treatment of Sin-ting or its disciplinary measures. 'The student was emotionally unstable and sometimes displayed uncontrollable behaviour. The arrangement was to meet [her] special learning needs as well as for the safety of other students,' he said. One teacher said the bureau did not talk to all the teachers during its three-month investigation. The Po Leung Kuk will interview all the teachers next week. But teachers who spoke to the Post said they were not confident Po Leung Kuk would be fair. Andrew Lam Ping-cheung, chairman of the Law Society's criminal law and procedures committee, said isolating a child in a confined area against his or her will was forced imprisonment and could constitute a criminal offence.