I have noticed over the years that there are two ways that students look at me in class.
When I am using English they seem far away. They seem to be considering what I’m saying but not really caring very much about it. I guess they hear enough English.
But when I’m talking slowly in French about them in a way that they can understand (i.e. using Walk Before You Talk, going ten times slower than I think is acceptable, pausing, listening to them, looking at them and really seeing them), then their their demeanor changes.