'Slave Letter Writing Activity' assignment given to eighth-grade students. (Amy Nobles)LOS ANGELES - A photo of a Mississippi middle school teacher’s writing assignment on slavery has gone viral and is drawing heavy criticism online, with many saying it trivializes and ignores the facts of slavery.The assignment was given Wednesday to eighth-graders at Purvis Middle School, where students were asked to "pretend like you are a slave working on a Mississippi plantation" and "write a letter to your family back in Africa or in another American state describing your life."Frank Bunnell, the principal at the school, apologized to parents in a letter, noting that the assignment was the last page of a purchased PowerPoint presentation that.