A dozen teachers in the United States have been thrown out of the profession, after a cheating scandal.

The teachers from Mississippi were accused of offering up to $1,000 to exam supervisors for help with competency tests at a college in Arkansas - and were among a group of 52 accused of cheating last year.

This is the latest example of teachers rather than pupils getting caught cheating - a trend which cheating experts say reflects the growing pressure on teachers.

The teachers were caught attempting to cheat in part of a teaching certificate required for working in a number of US states - and the 12 from Mississippi have either handed in their teaching licences or had them suspended or revoked.

The examination board called in the FBI when suspicions of cheating were raised.

Promotion chances

A more common form of cheating by teachers has been to unfairly interfere with the results of their pupils' tests - in an attempt to make themselves appear more effective as teachers and to boost promotion chances.

In New York last year, a special investigation found evidence of teachers becoming involved in the falsifying of primary school test results.

In the report, a 10-year-old pupil was found to have been made to cry by a teacher wanting him to copy down a correct answer in a test.

And an academic study of cheating carried out by Gregory Cizek, associate professor of education at the University of North Carolina, found that there were an increasing number of teachers bending the rules.

Again it was seen that teachers were becoming more likely to cheat as a way of boosting pupils' grades as a means of improving their career prospects.