Teaching a class is like performing on stage, you have spent your entire life perfecting your craft, (art) and now it is time to put it in front of someone that is wanting to receive what you have to give. they are actually paying to watch you "perform". When you make eye contact with a student and you are perfectly confident in your ability to pass on the knowledge that you have, it is noticed right away by the student, the same as a performer on stage is noticed to be a master at their art from the audience. You can tell when they know you know what you are doing, and they tend to respond much more favorably.