YAVA stands for you Ask, Volunteers Answers. Teachers do this all the time; I did it myself foe years. Questions are asked; hands go up, keen volunteers speak; the lesson can feel very lively; the teacher will often think that thing went rather well. For a couple of minutes, this is an active thing to do; but it has a very limited life. If you’re not volunteering, you know that no one is going to bother you. The keen participants at the front can do the work; all you’ve got to do is keep quiet and avoid the teacher’s eye. Don’t you remember doing that at school? I spent two years in chemistry staring at the grain on the desk while my fresh-faced chemistry mates rattled on with Mr. Webster abut molecules and compounds. Everyone was happy, including me.