MEHLVILLE, MO -- A class assignment landed a Missouri teacher on administrative leave and has the NAACP calling for a formal apology.It happened at an elementary school in Mehlville, Missouri. Students in a fifth grade class were asked to do an assignment setting prices for different things and then reflect on topics such as a free market economy and wealth.The students set prices for 12 different things: lumber, tar, wool, milk, etc. However, the last item the students were asked to set a price for was quite different from the first 11."You own a plantation or farm and therefore need more workers," the question began. "You begin to get involved in the slave trade industry and have slaves work on your farm. Your product to trade is slaves. Set your price for a slave. These could be worth a lot.""The assignment was culturally insensitive," principal Jeremy Booker said to KMOV in St. Louis . "The teacher has expressed significant remorse."Booker sent a letter to parents explaining the assignment and the steps being taken to rectify what happened and keep it from happening again."The school district is continuing to investigate this event," Booker said. "I am working with district leadership to provide all Blades teachers and staff with professional development on cultural bias in the near future."The NAACP called for a formal apology and offered to help train school staff.