Cheating in tests is becoming more sophisticated - and is increasingly being carried out by the teachers, says the author of an international study.

Gregory Cizek, associate professor of education at the University of North Carolina, has published what has been described as the most complete analysis of exam-room cheating.

Among the findings in Cheating on Tests are that 3-5% of exam candidates are likely to be cheating - with almost none of these pupils being caught.

A recent trend has been for more teachers to cheat - allowing their pupils to see questions in advance, correcting answers and "outright giving them the answers".

This has been prompted by increasing pressure on teachers to be seen to be successful - mirroring the pressures that encourage their pupils to cheat.

And wherever the opportunity to cheat increases, such as with laxer supervision, the rate of cheating was found by researchers to increase.

Professor Cizek's research found that cheating appeared to be a global phenomenon - with little cultural variation.

"Wherever the stakes are high and there is an advantage and an opportunity to cheat, it seems to happen."

In his study, Professor Cizek uncovered many sophisticated approaches to cheating - including an increasing use of technology.

Infra-red links between calculators have been employed and the "vibrating crib sheet" of a pager has been used to send in messages to an exam room.

Laser pens which pick out letters on a wall behind the back of an invigilator have passed messages to an entire class.

$400 pencils

Universities have become more aware of the risk of plagiarism, with hundreds of essays and assignments available on the internet, he says.

A more complex exam cheat involved using time zone differences and a coded message on a pencil. In this scam, a student in New York faxed the contents of an exam paper to another student in Hawaii who was taking the same exam on the same day - but at a later hour.

The answers to the multiple choice test were carved as a code into a number of pencils, which were sold to other students for $400 a piece.

Multiple choice questions were also the subject of other low-tech, but imaginative cheating efforts.

These included the strategic placing of different coloured M&M sweets by pupils - with their placing representing a coded message for the answers.

Another form of illicit signalling used by pupils has been the clicking of pens, spelling out a pre-arranged message.

Professor Cizek says that he is concerned at the apparent lack of enthusiasm for catching cheats. Pupils do not like to inform on cheats in their peer group and, the professor found, teachers were not keen to pursue or uncover cheating.