It's bad to judge based on race.
Mark and Jamal are working together on a group project.
Mark wants to get a good grade.
Mark splits the work evenly, and he and Jamal work together.
Mark assumes Jamal is not smart because he is black, so he does not give him any work to do.
The project is finished, they get a good grade, and maybe even become friends.
Jamal's feelings are hurt and the project does not get done.