Students plagiarising internet essay material in their coursework are using a form of 'self-teaching', says the director of the qualifications body.
Some do not understand that plagiarism is wrong - others do
One student told BBC Radio 4's Today programme over 50% of classmates copied net material to boost their grades.
Dr Ellie Johnson Searle, director of the Joint Council for Qualifications, said small scale copying still showed an understanding of the subject.
But she said full plagiarism, without listing sources, was wrong.
'Learning the subject'
Large-scale copying of someone else's work is picked up by the examining bodies and in some cases penalised, she said.
But she said pupils who simply copied odd bits of internet essays and used them were not heavily punished, and in most cases would be asked to rewrite the coursework.
She told the programme: "Pupils can change the language and grammar and put it into their own words, but if they are going to that sort of effort they are essentially self-teaching and are learning the subject anyway.
"They would not be able to make extensive alterations without an understanding of the subject."
A high school pupil who spoke to the programme anonymously said copying essays published on the net was easy and commonplace among classmates.
He estimated more than 50% copied work from the net - using sites specially set up with past essay material for exams such as GCSEs.
Policing methods growing
The schoolboy said he believed the practice was foolproof.
"Different pupils can all take work from different sites on the net, there are loads of them," he said, adding that some sites allowed you to write an essay in English and have it translated into French.
But Dr Johnson Searle said just as more sites are cropping up offering essays to copy, so the number of policing methods was growing.
Anti-plagiarism software is now available and is being used by some bodies, she said.
She maintained there was a big difference between pupils using large amounts of text from internet essays and re-writing small sections.
Essays submitted where the student had used chunks of unattributed material, but a good portion of their own material in the coursework, would result only in a warning, she said.
"Some coursework pieces which have actually been heavily reliant on other sources rarely reach the notice of awarding bodies," she said.
But she said teachers and lecturers were alert to incidents of plagiarism and copying.
"They know their pupils' style, their strengths and their weaknesses and use that knowledge to check authenticity," she said.
She said the Joint Council for Qualifications dealt with less than 0.1% of cases of plagiarism.
The ultimate penalty for blatant plagiarism was a ban from an exam board for a certain length of time, she added.