When Maya Saakvitne's parents sent her for a three-day school field trip two years ago at Nature's Classroom, a camp in western Massachusetts, they did not expect her to come home with a tale of her feet falling asleep after counselors asked her to kneel in the hold of a make-believe slave ship and keep her head down even though some of the other 5th-grade classmates from Jefferson Street Elementary School were crying. Nor that the same class later would sneak through the woods at night in a simulation of an escape along the Underground Railroad. When Maya's parents asked the Nature's Classroom staff to explain, they did not like the response. Representatives of the Charlton, Massachusetts-based nonprofit, which for 32 years has run experiential learning camps for school groups along the East Coast, said the simulations had good intentions. According to the curriculum for the Underground Railroad activity, the goal is "to encourage students to think and act in ways that Africans trying to escape slavery thought and acted," and to "create a physically and emotionally safe, yet challenging experience." The clash between Nature's Classroom and Maya's parents represents a vigorous national debate about the use of simulations--the recreating of historical and fictional events--as anti-bias teaching tools. Some educators claim simulations have unparalleled power in sensitizing young people to oppression. But others, including prominent diversity education groups, say it is time to stop. Simulations, they say, are both dangerous and unnecessary.