We had an international day at our school and some of my first graders started making faces at the food that some of the Korean American families brought. They kept calling the noodles worms and chanting, "We want American food." Their parents didn't stop them. How can I help them and their parents learn that making fun of someone else's food is wrong?
Sometimes schools use international dinners as a kind of a celebration of diversity, but unless these events represent an ongoing commitment to exploring and celebrating similarities and differences they may foster exactly the kind of behavior you describe. Unfortunately, when children are exposed to things or to situations that are outside the realm of their daily experiences they may cope with their discomfort or feelings of inadequacy by making jokes or banding together to make fun of whatever it is they perceive as different. If that happens, they need to be told to stop and also told that what they are doing is hurtful. What's more important, however, is to think of ways that you can prevent that kind of behavior or use such experiences when they occur as "teachable moments."
It is crucial to incorporate the similarities and differences among people into your classroom and your school throughout the year. If diversity is an ongoing part of children's education then they are likely to feel less threatened when they are exposed to new ideas or customs outside of their own experiences. In addition, in a situation like this particular one, you can prepare children for the different kinds of food that they might encounter at an international dinner, and also talk to them about your expectations for how they will behave. They do not have to like everything they are served. They don't even have to taste everything. But they can't make fun of it.