A sea of blank looks accompanied by silence--how am I supposed to interpret that? Did you not understand? Were you even listening? Are you in there? Hello?
Then a wave a laughter fills the room. No problem interpreting laughter: You got it! You really got it!
Two students who always come to class together, sit together, leave together, suddenly start arriving separately and sitting on opposite sides of the room. Ooh, trouble in paradise? Better not draw attention to the rift--I wouldn't want anyone to run from the room in tears.
A student in the back eagerly nods and smiles--at some brilliant point I've just made or at something she sees on the smartphone cleverly hidden beneath the desk? I can't see enough to know. Call on her for comment? Absolutely--and this time she has something interesting to say about the topic at hand. Next time, who knows?
They keep me on my feet, these students, forcing me to constantly scan for meaning in their facial expressions and body language. Reading the room is one of those essential skills I never learned in grad school but had to develop through experience, always aware that as I'm trying to read my students, they're trying to read me as well. Sometimes we get it wrong without quite knowing why, but when we get it right, the class and I work together like an improvisation team, building a beautiful learning experience.
And when we get it wrong? Well, there's always next time.