Thanks, you two.
JetLag, I like your signature. I noticed it the other day when I was reading through the forum & thought about writing it down. It captures the complexity of the feeling of the arrival of an idea.
Leila, I don't feel like I have much difficulty "reading" my students. I think it's a talent teachers need to develop; I've talked about it with a few other teachers. "Sensitivity." We need to be sensitive to how they are feeling, what they are understanding, when they get frustrated, when they need help. The students I've had have almost never had difficulty communicating these things to me, especially when it benefits them and me. A huge amount of that is through body language. If I see someone slumping down in the seat, or distracted by what's happening outside the window, or frowning, I go see if they need help.
However, there was one situation when I had a class with people from various backgrounds, and there were three Korean guys in it. They were the only three Korean guys I ever had trouble understanding, and I think it's because they were behaving in my class as they are expected to behave in a Korean school. In a Korean school, the students are expected simply to listen to the teacher, not to volunteer any information or responses, but just to passively receive what is being taught. It annoyed me that I could not read their facial expressions, because they had absolutely no facial expressions--that is, their faces were blank. So I often ask whether my students have understood something I've said, and I put on my "questioning" facial expression--raised eyebrows, slightly protruding chin--and look around the class for non-verbal cues (for example, nods) as to how people are responding to what I'm presenting, and from those three I got no response. It took me a while to figure it out: they were behaving in a way that was normal and appropriate to them. All the other East Asians I've had as students adapted to being in a new educational situation, and did their best to communicate with me.