It was a daring social experiment, even for 1968 - when teacher Jane Elliott first tried it in her third-grade classroom in Riceville, Iowa.
Elliott decided to explain to her children what prejudice was - by temporarily indoctrinating them into believing that the color of your eyes had a direct relation to how superior or inferior you were as a person.
A typical run of the experiment would span a few days. On the first day, children with brown eyes were told "they are the better people." They got praise from the teacher, treats, bonus recess time, and other rewards. The blue-eyed children, meanwhile, were met with the opposite - no recess time, no treats, and sometimes Elliott would speak to them in harsher, clipped tones.
Driving the concept home, the "inferior" children were made to wear collars so that they could be easily identified.
Elliott would observe what she saw, and each year she performed the exercise, the same results - the children would go from being the best of friends to the worst of enemies in the span of a few hours - and all because they were told certain people were better because of a trait they had no control over.
As the experiment went on, the roles would be reversed - the teacher would say she got it wrong, and that really the blue-eyed children were superior. The children who were once "on the bottom," she said, would relish the chance to see the others learn what they had been put through.
After both halves of the class had time to experience the highs and lows of the experiment, Elliott would talk to them about how they had just experienced discrimination, and why it is important to treat others equally.
ABC Television recorded Jane Elliott's 1970 third grade class as they went through the eye-color exercise. In 1985, the PBS series "Frontline" re-aired portions of the film and brought the children from that class together for a reunion - to watch and discuss what they had learned and how it shaped them in the years that followed.
"Frontline" also followed Elliott into her new role - performing the eye-color exercise with adults who believe they are being gathered for an ordinary exercise in human relations. Elliott is met with more aggression with the adults than the children, and the cameras continue to roll as tensions and tempers rise.
“After you do this exercise, when the debriefing starts, when the pain is over and they’re all back together, you find out how society could be if we really believed all this stuff that we preach," Elliott said.
In the decades since, Jane Elliott has performed her eye-color exercise hundreds of times for groups of teens and adults - even for the audience of The Oprah Winfrey Show.
In 2003, PBS posted the full documentary, "A Class Divided," on their website, saying that the title was at the time their most requested film.
This weekend, in the aftermath of the police shootings involving black Americans and the deadly assault on Dallas police officers, PBS posted the film to their social media outlets once again. Hundreds of reactions, shares and comments followed in the span of a half-hour.
You can click here to watch "Frontline: A Class Divided."