So what would her male classmates have then heard? There may have been a short continuation of her telling off, followed by the command to “bend over” at which point one of the boys sitting near the door may have said something like: “Yes, I think he/she is going to do it. He’s/she’s just told her to bend over!” A deathly silence would then ensue as the excited pupils listened even more intently. The tension in the air as they listened and waited would be gripping.
Then they would have heard the first whack, possibly followed by the girl yelling from the pain. At that point both boys and girls would sit there with mouths agape (girls tended to put their hands over their mouths at such moments) as they listened in shock to their classmate’s suffering.