Max (on the left) could work for this. He's a junior in high school, and he'd totally be the quiet kid in the back of a classroom, trying very hard to not fall asleep (if he didn't fall asleep already, he's a tired and nervous boy).
Or if it's a not-classroom scene but somewhere where people are standing up, then he'd probably be talking to thin air (actually talking to Dave but he's invisible to everyone else, being a ghost and all)
This is a pretty old reference but it still works pretty well. These guys are from Guardian Ghost