Usually we use the character's eyes to judge them (window to the soul or whatever) especially in this manga where theres multiple moments where we are literally forced to infer what the student might be feeling just from how his eyes are drawn in certain panels.
so by not having the reader see any shots with the teacher's eyes in it, we are almost given no clue of what the teacher's full intention might be in these scenes [well we do, but its more like in the sense that you feel ominous on what he'll do next cause you don't understand what this teacher might even be feeling/whats going through his head while doing all these]
Usually we use the character's eyes to judge them (window to the soul or whatever) especially in this manga where theres multiple moments where we are literally forced to infer what the student might be feeling just from how his eyes are drawn in certain panels.
so by not having the reader see any shots with the teacher's eyes in it, we are almost given no clue of what the teacher's full intention might be in these scenes [well we do, but its more like in the sense that you feel ominous on what he'll do next cause you don't understand what this teacher might even be feeling/whats going through his head while doing all these]