Sketching students focused in their work

I am not totally bought into drawing digitally yet, in contrary to all my friends' presumption. I actually draw more with pen on paper and on my newly bought iPad Pro, which is already about 1.5 months old. However, my time for sketching has been limited these days, as I am currently teaching several classes and 4 days in a work week. I would actually draw a little when I have assigned work to my students. Most of the time I would practice sketching them as they work.