There was a significant improvement in the overall performance of schools forced to switch to mother-tongue teaching six years ago, the Education and Manpower Bureau said yesterday. But the English standards of top students in Chinese-medium schools continued to decline. This year's fifth formers in Chinese-medium schools were the second batch affected by the medium of instruction policy introduced in 1998. The policy forced 300 of the 412 public secondary schools to adopt Chinese as their medium of instruction, with the belief that students would learn more effectively in their mother tongue. But the schools were allowed to switch back to using English to teach some subjects in Form Four and Five. The percentage of top students obtaining five or more passes in Chinese-medium schools this year has increased almost 5 per cent in two years, while the mid-ability group rose 3.4 per cent. The pass rates for subjects such as Chinese, mathematics, geography, history, economics and biology saw significant rises. Although improvements were noted in English language, the high-ability group failed to reach the level achieved before the mother-tongue policy was imposed. The analysis also indicated that low-ability students in these schools had fared worse in many non-language subjects. 'HKCEE results are just one of the many indicators to measure the success of the medium of instruction policy,' principal education officer Fanny Lam Fan Kit-fong said. 'When one looks at the performance of the low-ability students, one must take into account a string of factors that include their motivation to learn, peer support and socio-economic background.' Ms Lam said the English language performance of students in 80 Chinese-medium schools was higher than in 2002.