A good result is a ticket to a lucrative job

The developments have left Bangladesh's high school examination system in crisis.

In rural Bangladesh - where the problem is most acute - it is doubtful whether any of the results can now be considered valid.

Although cheating is commonplace at this time of the year, the latest bout of mass expulsions is embarrassing for the government.

It launched a high profile campaign against cheating shortly before the exams started, but the situation has only worsened.

Angry students

Throughout the country, there have been clashes outside examination centres involving students, political parties and police.

Some of the violence has been attributed to angry students who rioted after they were expelled.

Police have been guarding exam centres

In other cases, clashes began when police tried to stop unauthorised people from entering the exam hall.

Gunshots were fired in the air, and several people were arrested trying to smuggle notes to candidates inside the examination hall.

At least 15 teachers have been dismissed from their jobs, accused of helping students to cheat.

The government says that the problem cannot be solved until the country's education system has been radically reformed.

But, with a general election looming, no major changes are likely to be introduced imminently, especially when exam results are so politically sensitive.

The results of the latest papers will determine the future careers of over half a million students.

Scope for analysis

Schools which perform badly could have their funding curtailed by the government.

The Bangladeshi education minister, AS Sadik, said that one of the most urgent issues was to address the way exam questions are set.

He said that at the moment it is possible for cheats to secure high marks simply by quoting directly from a text book.

Mr Sadik said the questions should allow more scope for analysis, which required a change in the attitude of some teachers.