I TAed a compulsory "Introduction to Engineering" class at USyd. The class itself was dead easy, the equivalent of the fizzbuzz interview question.
The single assessment was "review an engineering article" where I caught 7 students (all international) plagiarizing. Not just borrowing a sentence or two, but lifting entire paragraphs and gluing them together with broken English. In one case a student had gone as far as submitting Stephen Hawking's "Space and Time Warps", verbatim.
I raised all of these to the professor. Despite all students signing the "I know what plagiarism is, I won't do it and understand there I will be kicked out if I do" - the professor knocked back all of my claims and all students passed.
It was a huge disappointment to realize that this is how the "education system" works.
I don't know how well it holds up for large groups, but for ~5 or so clients it has worked nicely for me.