The other day, right as we were in the middle of our starter, the principal walked into the room, strode purposefully to the back of the room, and sat down. A bit of a hush fell over the class at a time when I do not require complete silence–they’re doing pair work, after all. Still, everyone was especially quiet.

A principal observing a classroom is the perfect illustration of the bane of modern science: the inability to observe something without changing it in the process of observation.