More than half of teachers in school sixth forms and colleges think internet plagiarism is a problem. And only just over half of respondents to an Association of Teachers and Lecturers' survey thought that students understood what counts as legitimate research and plagiarism.
About a quarter did not believe their institution had a policy for dealing with the issue.
Views on the matter varied between the 278 participants in the survey.
One sixth form English teacher in Wiltshire, previously a fan of coursework, said he now wished it would "disappear entirely". "There is a tension," he said, "between wanting to be rigorous and not wanting to put my own students at a disadvantage when competing against other candidates whose teachers are not so scrupulous."
However, one sixth form tutor in Dudley, West Midlands, disagreed. "If teachers are sufficiently engaged with students, it is very clear what they have produced themselves and what they have copied from elsewhere," he said.
One teacher in a further education college said about a third of students submitted work from the internet for GCSE coursework on Of Mice and Men and Romeo and Juliet. Two students submitted identical essays.
Mary Bousted, general secretary of the Association of Teachers and Lecturers, said she supported the use of coursework in assessment.
However, she added: "It is still very concerning that so many students do not seem to know the difference between legitimate research and plagiarism from the internet."