I've had to grade quite a few essay papers in the classes I've taught, and I've suspected some may have plagiarized but I never really pursued check on them because it would be too time consuming to check their sources and pursue any/all possible sources where they may have copied from.
What's the easiest way to check for plagiarism? Is there a search engine tool that one could use to upload a paper and check for it? I doubt it, but other than that, I don't know of any other way to check for it than to put in more effort than I have time for.