One child in my class is Cambodian and the rest are Caucasian. I don't know whether to talk about his similarities to and differences from the other children or downplay them.
Sometimes in a large-group setting it is difficult to be the only person from a particular background or the only person with a visible disability. Many adults who endured this situation when they were children recall diversity discussions with anguish. "I always wanted to hide under my chair" is a common refrain. If you celebrate diversity in the classroom throughout the year with music, books, games, crafts, posters, and other materials, the child will feel less singled out when the topic arises. Take your cues about how much to talk about the child's heritage from the child, but whatever you do, do not make the child feel that he is the spokesperson for all Cambodians. Within every cultural group there are similarities, but there are also numerous differences. Use your discretion to decide whether it also might prove useful to talk with the child's parents. They might be excited about discussing their culture with the class.
Remember that even if all of your students are white, chances are good that their ancestors came to the United States from different countries. By acknowledging and exploring all of the cultures represented, you can help children accept and embrace the differences between them.