Thomas Chan Chi-Sum, an assistant director at the ICAC, said aided schools were most likely to be victims of corruption because they received donations from many sources and would buy more services from the private sector.

Typically, a headmaster would be approached by a text book supplier, school uniform manufacturer or caterer and offered a bribe to take that company's services. Sometimes triad gangs might be hired to threaten the headmaster.

During a court case last November, at the end of which a headmaster was jailed for taking backhanders to buy books, it was claimed that bribery was accepted as a traditional incentive in Chinese business deals.

On the advice of the ICAC, the Department of Education has circulated guidelines on accounting practices within schools which spell out the purchasing procedures that headmasters should follow.

It advises that school management committees should approve all purchases and that tenders should be sought before anything is bought.

However, there is still scope for a crooked headmaster to accept donations to the school and put them into his own pocket. One area open to abuse is the hiring out of school facilities, such as the assembly hall, to outside organisations for private gain.

Another is the dishonest running of school trading operations.

So far this year 12 complaints about schools have been made to the ICAC, of which four are pursuable.

''We would like to see more controls so people don't become corrupt,'' said Mr Chan.

''But we are aware of a recent Government initiative which is to give the schools more power under the public sector reform package.

''Against this background, we have recommended to the Education Department that it should give the schools more guidelines. But the ultimate control must rest with the school management committees,'' he added.