Some British university examined a student who might have plagiarized his/her essay

Apparently some British unis put a student through an oral quiz of a paper's content if they suspect the essay has been purchased. Anyone ever heard of that happening to one of their clients? I've never heard of it happening in the U.S. although theoretically it could..

No UK universities take oral test. I have never heard of any such thing

Never heard of a formal "oral test" taking place as a result of plagiarism however, if a lecturer suspects plagiarism it may be quite normal practice as part of the investigation to call the student in for a "chat" about the content of the paper. If the student has handed in the paper without even bothering to read it such a "chat" is likely to reveal that the student did not write the paper.

I guess that's what I was thinking if, pretty much. Do you hear of it happening very often?

In the U.S., my understanding is that the instructors can do that, but they don't consider it good enough proof of plagiarism even if the student fails the "chat."

If you are talking about Viva Voce, I have seen quite a number of requests from students who ask for "summaries" and anything that can help them internalize the paper. For example, they may ask for a log detailing the research process so that they are able to demonstrate that they took time to construct the paper. In fact, I do not think this is a practice confined to the UK or US-it is a general practice in most Western Universities because how else would the originality of a paper be established.

Yes, viva voce. So from what you are saying, it sounds like even viva voce can be beaten with the right preparation.

.. Especially when the student can't define a word or phrase used in the paper, apart from any substantive knowledge about the topic. I'd say that's pretty conclusive proof of plagiarism in one form or another.

I don't know how common it is across the board. The first University I went to was very strict on the issue and I know of students who were asked to discuss their papers further with a lecturer. However, some schools (including some very good ones) don't care less they need the money from overseas ESL students and seem to overlook the fact that a student who barely speaks English can turn in a native quality essay. I suspect this will continue while funding is tight but that's my opinion rather than a statement of fact.

My experience working for ESL and native student tells me that for ESL students, the standards of a good university/school/college are considerably lower as compared to those for a native student.

You mean the ESL students can get away with a lower quality of work?

Yes, I do.

Sometimes the students themselves cause the question as to whether or not they wrote their paper because of the quality of their earlier work. If they are so bad when it comes to the written assignment at the start of the semester, then they show a sudden improvement mid-stream, almost as if they gained writing talents over night, then their work will definitely be questioned and so will they. The professors tend to take such sudden changes are red flags. This leads to the eventual questioning of the student since the previous work of the student does not show any signs that such writing talents exist for him. This is precisely why I used to always advice my students to come to me at the start of the semester or soon enough into the new semester. Basically, I tell them, they can attend the classes and participate in discussions. However, when it comes to their written homework, they best let me handle it for them immediately. That way the chances of their being questioned regarding their writing ability becomes limited from the very start.

It has become common practice for professors in specific subjects to quiz the students on the papers they submit. This is usually the case with a thesis or dissertation defense. The professors figure out if the student wrote the paper or not based on the way they act during the procedure. Viva Voce isn't the only time the student needs to be able to defend and explain his research process. Since the professors have become wise to the writing services. They often employ an oral report or question and answer when a formerly bad student suddenly starts performing well in reports and essay presentations. Yes, it becomes suspicious when the student improves overnight.

These days professors assume that they essays are plagiarized via AI and make the students prove they did not plagiarize it. Some have taken to no longer providing homework and instead, having the students write their papers, using pen and ink, in the classroom, even if it takes all week. That is the only way the professors think they can stop plagiarism via AI or pre-written essays. Even with all the anti plagiarism software available today, a teacher can no longer be sure that the paper is truly original. No matter what the software says.

Eventually, educators will realize that assigning out-of-class essays serves little purpose, in the first place, for students in the vast majority of all major courses of post-high-school academic study.