I have seen students make fun of another student for having body odor. It is so discomforting to see. I would start by sending a respectful letter home to the parents or ask if they were able to meet for a conference. Whichever method you choose, I would make sure to center the conversation or point around the child's well-being and feelings. Let the parents know that other children are making fun of their child because of his body odor, and even though that could be culturally acceptable from where they are from, you do not want it to affect the child emotionally because students are teasing him about it. I would then let them know how well he is doing in the class and how bright and willing to participate he is. Make sure to enforce that you would not want the teasing to affect that either.