When you have to face the consequence of your actions it´s hard to be on the other side, but the rule applies to everyone. (including us - you, me, the others.) So, you are going to be subject to the following sanctions...
And other ways, but the gist of it is, in average, the above one.
In fact, it seems that in English-speaking countries they do enforce rules in a direct way, so the language would match this policy. My feeling here, is that they don´t usually soften their statements.
As we do (with "Eu vou dar uma punição para vocês, caros alunos..." - as if being so sorry for the student´s fault, and as if we are to blame for their fault.
Obviously, there are cases and cases, and the adressing would vary from people to people, but my impression is that they are more inclined to call a spade a spade.
Anyway, I´ll leave the ball on the natives and experts´court, as I said "it´s my feeling" here. Plus, the times are changing, the other day I saw an item on the Reader´s Digest about the "cheating generation" of today". And the parents that doesn´t admit or accept that they cheat!
By the way, the more authority you have, the more soft speaking you are, the teacher should not let them to reach the point which the students are on the charge! It seems like that, from the sentence it seems like the teacher is already on the back seat!