What is the main conflict in You Can't Say You Can't Play by Vivian Gussin Paley?

You Can't Say You Can't Play is the story of Kindergarten teacher Vivian Paley's attempt to teach her class not to treat some children as inferior to others by systematically excluding them from playing with others. Paley sees this process of exclusion hardening as children age, and continuing long into adulthood. She believes that if children can be taught to treat one another as equals no matter what, this lesson could follow them throughout their lives