There will always be a few students who try to cheat on exams and unfairly bump up their results.
And with school pupils now carrying phones with them, teachers have got to be extra vigilant to spot those who might be tempted to turn to the internet for a helping hand.
But one teacher has found a brilliant way to catch out their students, and the video has been watched more than one million times on TikTok.
It shows a room full of pupils taking a test, with stacks of books piled on the desks to hide their answers, meaning it would be easy for anyone to sneak a glance at their phone without being seen.
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But the teacher is one step ahead, and simply walks into the room and quickly flicks the lights off - with one student's phone lighting up his face, forcing him to hand over the device.
It racked up hundreds of comments as one person said: "This is so smart omg" and a second wrote: "I won't even be mad."
It's not the first time a teacher has out-smarted their pupils after another became fed up of students leaving the exam to "use the toilet", knowing that they were really looking up answers.
A student in the class explained that the teacher knew the website their classmates were using to cheat and put a question in the test that was illogical and impossible to solve.
A month before the exam, he got a teaching assistant to pose the problem on the website, where he anonymously replied with an answer that was incorrect and "very unlikely that someone would make the same assumptions and mistakes independently".
From the 99 exams handed in, 14 of them fell for the trick and gave the exact answer their own teacher had posted online.
All were given an overall score of zero and reported to the university, while the students who didn't cheat were given full marks for the bogus question.
