I think a large part of it is the age of the students. Younger students seem to be less communicative, even in person. Where as older students are more confident in themselves; and are willing to participate more even if they don’t know the answer.

I took a matrix-based carbon modelling course over the summer at another university to help my own research. The course used break-away rooms and I found it extremely helpful to talk with and meet colleagues from other universities with other backgrounds.