Take into account that it is a teacher. The future of students is at stake here. He is dealing with kids or young persons and he is purposely creating distress

Take into account that it is a teacher. The future of students is at stake here. He is dealing with kids or young persons and he is purposely creating distress when the goal was to educate. Even if it is not good for students to cheat, the way he dealt with that will have probably ruined a few students lives. Think about that... And also take into account that him and the institution have created the conditions leading to these students cheating. If you have empathy you can easily guess that it is possible that some of the caught students were not 'bad persons' but just did it because they had the opportunity and on the other side a lot of pressure (future depending on the success of this exam, family poverty, violent family pressure to not fail). It would have been better to do this thing as an educational move / warning to show the concerned students that there is a risk cheating. And also using measures to avoid cheating in the first place: taking phones, not letting students go to toilets in middle (this is common) etc...