On the left side, ask them to list the racist stereotypes aimed against their or other ethnic groups On the right side, have them list people they know that don't have these stereotypes, then discuss why you can't generalize characteristics to certain groups. Have them not sign it, but hand it in, then have other students read them out loud and discuss them with the students. This will help the student reading it to learn empathy, as well as the students who discuss it. A generalization used to define a whole group of people based only on the words or actions of a single member of that group.
Separation perpetrates myths.
Just having that person around will acclimatize the students and that alone is valuable teaching. Celebrate the ethnic holidays of the various students in your class and discuss what each holiday means. Make it fun, with food, costumes, etc., so that students learn what they have to learn from others is interesting and their lives are all the more richer for it. Discuss the images of various ethnic groups shown in movies and t.v. Also, discuss lyrics of various artists' songs.