Sir John Colfox Academy, in Bridport, was the target of hackers, believed to be from China, after a member of staff mistakenly opened an email that contained virus and infected the school’s entire computer network. The email claimed to be from a teacher at another Dorset school.

Hackers seized pupil’s GCSE courework of the secondary school and demanded cash or returning it.

The Sir John Colfox Academy has about 1,000 pupils. The coursework was from one subject submitted by Year 11 students, which was saved on the school' system.

Head teacher David Herbert said: "We are liaising with the relevant exam boards about this specific issue."

Police have launched an investigation into the cyber attack.

Neither police nor the school have said how much money was demanded for the return of the coursework, but police say no money has been paid.