About 10 yrs ago, I had 3 students in my chem class from Saudi Arabia who:
- could barely speak English (this is relevant)
- would fail my weekly quizzes miserably, using nigh incomprehensible English when they had to explain an answer.
- aced my first exam (3 highest grades!) using idiomatic English in all of their explanations (and they used the same idioms!).
Obviously, they were cheating. It's far too complicated to explain how they cheated, but man oh man my Dean did not want to hear about a group of cheating foreign students.
The Dean never told me that I couldn't fail them (I did fail them), but he did not want me to bring this 'problem' to him--and I could tell that if there were any political blow-back associated with their failing grades, it was going to be 'my fault.'
The main cheater even emailed me near the end of the semester and admitted he cheated, but explained that if I failed him, he would have to stay an extra semester to complete the course.