The head of the Hong Kong Institute of Education's department of English, Andy Kirkpatrick, said it was difficult to say whether fine-tuning the language policy would improve students' English levels.

'It's unlikely. You'll get more pressure for classes to be taught in the English medium; that means more teachers have to teach in English,' he said, adding that he was not sure the city had enough teachers with the necessary skills.

The English language requirement for content subject teachers would be very high, and they would need extensive training, he said.

A very high standard of English would also be demanded of students.

'Kids are doing very well on content subjects through Chinese. It may be disadvantageous for many kids to learn in English,' Professor Kirkpatrick said.

'To increase English levels, there are many ways of doing it, such as having better English classes and interesting cross-culture classes being taught in English'.

Chinese University chair professor of educational psychology Hau Kit-tai said the adjustment was 'not necessarily going to raise students' overall English level'.

'There is no direct relationship between the two matters,' Professor Hau said. 'Language policy is very complicated and there is not going to be a perfect solution. In terms of raising students' English levels, it's a separate issue.'

Education lawmaker Cheung Man-kwong shared the academics' views and said the government was moving in the wrong direction.

'The government should have used a direct approach of implementing small-class teaching of the English language subject in primary and secondary schools. This would improve teaching quality and enable more class interaction,' he said.

A drastic improvement in students' English standards could be observed 'if this can be carried out consistently for 12 years', he said.

'Using English to teach content subjects might sacrifice students' performance on these subjects. It's not worth it,' Mr Cheung said.

The policy would be extremely unfair on teachers for such subjects, as their workload would be doubled, he added.

'This is hurting the professionalism of teachers and putting huge pressure on their language requirement,' Mr Cheung said.

But Association of English Medium Secondary Schools chairwoman Rosalind Chan Lo-sai argued for the policy. Having all academic subjects taught in English was key to improving students' English levels, she said.

'The number of students receiving bilingual education can be doubled overnight. This is vital to the survival of Hong Kong as an international city,' Ms Chan said.

'It'll greatly increase the competitive edge of Hong Kong.'