Some ideas for instilling cultural and social values in an elementary classroom with underrepresented students include celebrating non-American holidays. For example, you can create a calendar in the classroom that marks the dates of different holidays that celebrate other (i.e., not mainstream American Christian) cultures, such as Kwanzaa, Carnaval, Chinese New Year, Eid, Diwali, Yom Kippur, and so on.
Additionally, you can teach children about specific aspects of different cultures, using projects like international dishes or art forms (e.g., origami). This will not only expand the multicultural understanding of students, it will also allow them to learn new skills and hobbies.
Another effective way to teach elementary students social and cultural skills is by teaching the basics of a foreign language, such as Spanish or Mandarin. This will not only teach them new talents, it will also help them develop their communication and socialization skills. An enjoyable and easy way to teach a new language is to have them read children's books in a foreign language that also contains the English translation.