Teachers have called on the government not to relax anti-Sars guidelines for schools, despite the lifting of the WHO travel advisory last week. The call comes in response to the Education and Manpower Bureau's announcement that it would revise its precautionary measures this week. The guidelines, in place since early last month, require all teachers and students to wear masks and have their temperatures taken before school each day. School facilities have to be disinfected regularly throughout the day. Secondary school teacher Ho Hon-kuen, who is vice-president of the lobby group Education Convergence, warned against a sudden relaxation of the guidelines. 'Schools should not dispense with the precautions until Hong Kong is no longer classified as an infected area, which means no new infections for 20 days. New possible cases have been uncovered in Canada a week after its travel ban was lifted. The same could happen to Hong Kong,' he said. Mr Ho said the relaxation of the guidelines should not go further than allowing students to take off their face masks during physical education and music lessons. 'The bureau also needs to set long-term guidelines that require teachers and students to wear masks even if they only have a cold,' he said. Adalbert Vogt, headmaster of the German Swiss International School, agreed: 'There is no harm in continuing with the existing guidelines for another few weeks. It is better to be safe than sorry.' But Lam Seung-wan, committee member of Hong Kong Primary School Heads' Association, said the guidelines should be relaxed if the number of infected cases continued to be below five every day. 'Wearing masks should be made voluntary as teachers find it really difficult to teach with the mask on. Instead of checking every pupil's temperature, teachers should only do so with a sample of them,' he said.