Be aware that many students may not know what is considered common practice in American schools. They may not know about what you consider common knowledge.
Know different cultures norms regarding eye contact, notions of modesty, ways of ordering of time, conversational patterns, approaches to problem solving, preferences for competition cooperation, and conceptions of beauty and status and mobility and how they may affect a child’s comfort and attitude in the classroom.
Be careful to avoid generalizations and stereotypes of larger cultures such as assuming an Asian student celebrates Chinese culture and Chinese Holidays, many Asiian students may be of cultural backgrounds that are unrelated to Chinese culture.
Be careful to represent cultures accurately not based on commercially derived versions of holidays.
Know your students' religions and religious practices that may come up during the school day.
Acknowledge different religions holidays and show that you understand it is a special day in the students culture.
Understand and be aware that many of your students do not come from singular cultural or linguistic backgrounds. Their experiences in different cultures will influence their expertise.
Not all ELL students are immigrants. Many are born in the US.
Don’t try to make students assimilate quickly, acknowledge and integrate their culture into their experience in your classroom.