My father is deaf. He was great at reading lips and never learned out to read sign language. But, I always appreciated when people would recognize that he couldn't hear and they would take the extra time to make sure he knew what was going on. It meant a lot to me that people would care enough to help him out.
When I saw this video I immediately burst out into tears. A kindergarten class in Tennessee learned how to sing Happy Birthday in sign language so they could give a special birthday wish to their friendly deaf janitor.