My attitude to plagiarism is that it is something that needs to be addressed directly. It is not something that you can leave to chance. Students do need to be taught explicitly how to avoid it. It is also something which needs to be worked through. You can teach students how to use citations, for example, using the Citations and Bibliography tools in MS-Word, but students find it hard to understand why they need to cite, and of course when citation is necessary, and when it is not.
The issue is uppermost in my mind because my grade 8 students are currently starting a major project designed to teach and assess their ability to use citations and avoid plagiarism. The project erquires a Turnitin report to be submitted. My school has a Turnitin account, and many of our teachers require students to submit a plagiarism report when they submit an essay. Turnitin is very effective, but is does cost, and this is always an issue in any school environment. I recently came across a site called Paper Rater, which is absolutely free. The site is very easy to use. You literally cut and paste a paper in the relevant window and click on a Report button. You then receive ratings on spelling and grammar issues as well as a plagiarism rating. The engine even grades your paper!
The reports are extremely user-friendly, and are aimed at students rather than teachers. I have no idea how accurate the plagiarism detection engine is, or how it compares with Turnitin, but I believe that it addresses at least one key element in eliminating plagiarism, and that is that of awareness.
Because it is so easy to use, and requires no registration by students, it should encourage students to use it as a checking device ahead of submission. A drawback is that you cannot print out the report. I actually like this though. It provides, I think, a sense of anonymity around the issue, and allows students to get feedback on their writing without having to formally submit a piece to an engine like Turnitin, where the settings are controlled by the teacher, and are somewhat opaque to students. Students worry about whether they can re-do the report after editing their work to remove instances of plagiarism. In my experience Turnitin is not totally transparent in this regard, and teachers are not always aware of the implications of which tick-boxes they tick. I can imagine students taking ownership of Paper Rater, on the other hand, and this is probably a good thing.
I’m not suggesting that Turnitin should not be used. It is a great tool for generating a formal report, but it is not very student-friendly in its approach, and Paper Rater seems to fill that gap!