When the children arrive at class or club, first tell them that you’re glad they came. Then look for something new about them such as a new haircut, clothes, jewelry or glasses. Comment on how nice they look with it. (Don’t lie, though. You may have to settle for, “I see you got a new haircut.”)
Noticing little details about someone’s appearance tells them that they are important to you and can often tell you something new about them. It’s a good exercise in observation for you, the teacher, that can also help make you more alert to other, more significant changes such as changes in their countenance and attitudes and will help build that rapport with each child.