The act of voyeuristically viewing - or being viewed - via a small window within a door when confined to a teachers office for some reason.
The specific emotion felt by the exhibit behind the glass often correlated with the events preceeding their quarantine. Acts of malfeasance made one feel pleasingly notorious when regarded. By contrast, emotional outbursts or displays (particularly in response to taunting) engendered in the tank occupant a unique nakedness and vulnerability.
But most pleasingly, from the perspective of the viewer performing the tanking, was the fact that a swift gurn over the teacher's shoulder through the mesh-reinforced glass would light the blue touch-paper on a further outpouring of hysterical belligerence from the 'fishie'.