grasp of the subject is surprisingly shaky, a new study suggests.
Children in the former British colony were ranked first in the 2003 Pisa study conducted by the Organisation for Economic Co-operation and Development.
But Francis Tsang, a Hong Kong examinations official, and Tim Rowland of Cambridge university, told the conference that the maths knowledge of the 138 teachers they tested was "relatively shallow".
Many teachers seemed not to understand the questions, which covered basic arithmetical competence, geometrical knowledge and mathematical exploration and justification.
They found it particularly difficult to explain or justify their working.
In general, staff who did worst in the test had left school with only the equivalent of a GCSE pass - the level that just over half of the teachers had reached. But some of the more experienced teachers also did relatively badly in the test.
The researchers believe this was because most in-service training focuses on teaching methods rather than subject knowledge.
The teachers' inadequate subject knowledge may explain why school inspectors have found that primary staff tendto focus on basic computational skills, avoid group activities and seldom ask open-ended questions in order to generate discussion.
Hong Kong's administrators are now aware of the gaps in teachers' subject knowledge and intend to deploy more specialist teachers, not only in maths but also in Chinese and English.
The researchers said that this policy, which is also being adopted in Israel, is probably right for Hong Kong.
But they added that the minimum qualifications for maths teachers should also be raised, and that both initial and in-service training should be improved.