This just had to come first. It's unforgettable!
Mrs. Rosângela Oliveira, who was my Sociology teacher in 2000, taught this class at the end of the term, and I managed to addapt it to ESL classes successfully.
At the very beginning of the class, you tell the students that they will have to keep their eyes closed for a few minutes. During this time, they can talk freely (just choose the subject). However, when told to open their eyes, they cannot speak at all. While students have their eyes closed, make a small mark on each student’s forehead with some watercolor. Mark three or four students with white, two or three with green, following the procedure with different colors according to the number of students and, finally, mark only one with black. Next, tell them that they will open their eyes and, right after that, they have to FORM GROUPS (say just these two words) using body language, gestures etc but they cannot say a word. Wait and see what happens: in a few minutes, they will have formed groups of students of the "same color"... The one with the black mark will be alone. They will probably be curious and excited about their groups...
This is the time when the teacher explains the goals of the class. First, when they were told to form groups, they didn’t have any specific instructions so, by instinct, they grouped themselves based on the color mark on their foreheads (you can talk about sense of equality, need for acceptance); next, the student with the black mark ended up alone (prejudice, racism, not accepting the difference). Finally, you have them in groups of 3 or 4 to have a debate on why these things are so common and what should be done to improve this situation in society.
In all the times I’ve done it, the results were nothing but great, giving students not only an opportunity to speak about important matters but also a chance to reflect upon such flaws on people’s behavior.