Under the system, which is currently being introduced into public exams in phases, students' scores in classwork tasks marked by their own teachers count towards their final grade. The aim is to reduce the reliance on make-or-break final exams.

However, the push to introduce SBA into the Chinese and English language Hong Kong Certificate of Education Examinations has sparked controversy over a perceived increase in teachers' workload and questions over the possibility of biased marking.

But Dr Carless, saying he had no direct working relationship with the Hong Kong Examinations and Assessment Authority, said there was scope for teachers to integrate school-based assessment tasks with other components of the curriculum.

'Integrating the SBA preparation with some other elements in the curriculum can create useful synergy to avoid duplication,' he said.

He said he believed SBA should count for a larger portion of students' final marks in English, and could replace external oral exams altogether.

'You have two separate oral examinations. Why not phase out the external oral exam?' he asked.

'The SBA in English is a lot of work for only 15 per cent of the total mark. If you increase the weighting to 30 per cent, you can not only make the workload more efficient by eliminating the external oral, you can also align the value of efforts put in by teachers and students with the amount of work. I strongly endorse this recommendation.'

He said there was ample evidence that teachers could mark students' work reliably.

'Teachers have been grading HKCEE for many, many years. The only difference is, in SBA you have more teachers doing the grading work,' said Dr Carless, adding he believed Hong Kong teachers were qualified to grade students' work internally and externally.

Evelyn Wong Mei-chu, English-language teacher at Ning Po College in Kwun Tong, said SBA would work better for her students, who felt intimidated speaking English in an unfamiliar environment.

'We have to rethink whether the purpose of oral assessment is a test of students' real speaking ability or the ability to speak in an unfamiliar environment,' Ms Wong said.

However, Jonathan Lai Ping-wah, principal of Lee Kau Yan Memorial School said expanding the proportion of SBA in public exams would incur excessive administrative costs.

'The extra server space, information technology specialists and video equipment that are required to record students' performance during SBA will cost schools a lot of money,' Mr Lai said.

Stanley Ho Sai-mun, convenor of a task group on the new senior secondary curriculum under the Association of Heads of Secondary Schools, said there needed to be a review of the 'accumulative impact' on students if SBA tasks were to be increased under the new curriculum.

A spokeswoman for the exams authority said it had no plans to adjust the current system or to replace the public oral exam with school-based assessment in the Hong Kong Diploma of Secondary Education Examination when it is launched in 2012.