I agree. I liken the classroom to a theatre stage. No matter what is going on in the instructors personal life, when the lights come on, the smile comes on. The students are investing a lot of money to attend classes here, and the last thing they want to see is a dismal face.
A friendly face helps all people feel more comfortable. One of the things we are refocusing on concerns customer service. There is a lot to be said for smiling; saying hello; how may we help you; is there anything else, etc.
Other actions such as escorting a student to a department rather than giving directions or fully describing processes go a long way to making the student feel that they really are valued. That certainly impacts out retention.
