More than 100 schools and colleges have turned to the computer software universities use to combat plagiarism because of growing alarm at sixth-form pupils cheating in their coursework.
Almost all universities in the UK use Turnitin - the world's leading plagiarism-detection software, which is provided by the government-funded Plagiarism Advisory Service (PAS) at Northumbria University.
But amid fears younger and younger students are picking up the internet plagiarism habit, about 40 schools and 70 colleges have signed up for the software. It costs schools between £300 and £400 for 12 months access to the Turnitin database, which cross-checks work turned in by students with material found online.
Yesterday a survey of 278 teachers by the Association of Teachers and Lecturers (ATL) found more than half (58%) thought internet plagiarism was a big problem. Of those, 72% said up to half the work returned by their sixth-formers included material copied from websites.
A teacher in Leeds told the ATL that one piece of work was so "blatantly cut and pasted" it still contained adverts from the web page it was taken from.
The ATL's general secretary, Dr Mary Bousted, said the survey highlighted the risk of putting so much emphasis on passing tests and getting high scores.
"Unsurprisingly, pupils are using all the means available to push up their coursework marks, often at the expense of any real understanding of the subjects they are studying," she said.
The ATL said schools must introduce robust policies to combat plagiarism, but exam boards and the government should help them with resources and techniques for detecting cheating.
PAS director Will Murray said there had been a huge increase in websites offering sample essays, but Google had banned them. Many have now transformed into essay "banks" of model answers.
He agreed that pupils often do not know they are plagiarising when they collate work from the internet for an essay.
Barclay Littlewood, director of Academic Answers, the holding company for essay-writing websites such as ukessays.co.uk and a-level-coursework.co.uk, is to defend the services at the third PAS plagiarism conference this summer.
"[Students] should use us as another resource and as model answers before going on to do research to create a 100% original piece," he said. "We don't want to attract cheats."
A report from the Qualifications and Curriculum Authority (QCA) in 2005 said exam papers should be scanned. In 2004, 3,600 pupils were caught breaching the rules. A spokeswoman said the introduction of controlled assessment in GCSEs would increase public confidence. New specifications will be taught from 2009.
Schools minister Jim Knight said: "We will work closely with teachers to develop even more effective and reliable coursework assessments."