There is a great deal of good stuff on the web about why students plagiarise, procedures for detecting it, and dealing with it (see link at the end of the page). This page is simply about plagiarism-proofing your assessments when you set them, and hence forestalling at least some of the problem.
It appears that many students plagiarise out of ignorance, and although that may be a rather benign (as an old cynic, even naive) judgement, it underlines the importance of teaching about it and the conventions of referencing.
- Many institutions must seem to the student eye simply to take a big stick to the issue (often wrapped up in the verbiage of regulations students are given but never read).
- So offer to help. Clarify when you introduce the assessment that they know about plagiarism, its nature and penalties. (OK, you get the rolling eyes and, "Yeah, whatever." response), but also offer to help with anything which is not clear, or point them to named learning support or library staff who can help. Yes, there's an element of backside-covering (is that a PC expression?) here, but some students might actually take you up on it.
- Set assignments with a view to the possibility of plagiarism, so as to forestall it.
- Don't re-use old titles or examples.
- Very few students go for the custom-written assignment option (which seems to be pretty poor value anyway) but far more are likely to search the net for material. There is of course no problem in that as long as they attribute it, and don't use too much. So do it yourself. Put yourself in the position of the potentially plagiarising student and see what you can come up with on Google. (There may be more focused search engines, but Google is usually the first resort.) Make a note of the results for future reference. If there are too many, change the title. If there are a few obvious ones, why not recommend them in a briefing note on the assignment? Only the cheekiest plagiarist will give you back (unattributed) what you yourself recommended!
- If you are teaching in a professional area, especially one with work placements, set a title which requires the use of students' own experience. If that experience is likely to come from a placement, request that the supervisor/mentor sign off that it is genuine.
- If you are teaching in an academic area, consider requiring discussion of a supplied paper which is not likely to be readily available. You can even write it yourself.
- Getting really devious—potentially "descending to the same level" as the plagiarist, and hence forfeiting the moral and academic high ground, attribute the "paper" to fictitious authors, so that they will not curry favour by agreeing with you. Of course, at an advanced level, you can ask for critical comment on a real draft paper.
- Use a learning contract. This—apart from its other virtues—requires the student to present in advance an outline of the intended submission. If what you eventually get is substantially different from what you both signed up to, you have a clear basis for pursuing the matter. Jude Carroll (see below) also recommends requiring students to keep their drafts and notes so they can be examined if necessary. As she points out, it might actually encourage to do some drafting, too!
- Make the marking criteria explicit and transparent, including "use of sources".
And of course set assessments which require the higher reaches of Bloom's taxonomy. Sheer knowledge is easy to plagiarise; application and beyond is much more difficult.
Go here for a short video of Jude Carroll (probably the world authority in this field) talking about combating plagiarism, at the University of Nottingham, 2006. (Lots of other good video material on this site too.) Here for a downloadable good practice guide by Jude Carroll and Jon Appleton (2001) See also Carroll (2007)