Officials at the Sept. 11 memorial said Monday that one of their security guards shouldn’t have stopped a North Carolina middle school choir from singing the national anthem on the memorial plaza. “The guard did not respond appropriately,” said the spokeswoman, Kaylee Skaar. “We are working with our security staff to ensure that this does not happen again with future student performances.” Some 50 students from Waynesville Middle School in western North Carolina were at the Sept. 11 memorial Wednesday and had just started singing “The Star-Spangled Banner” when a guard told them to stop. Teacher Martha Brown said Monday that a different security guard had given the OK for her students to sing. But the second guard said, “You just can’t do this. You’ve got to stop now,” Brown said. “So we very reverently and quietly stopped what we were doing and complied with his request and quietly exited the park.” Video posted on Facebook by an adult on the school field trip sparked outrage and led to an invitation for the students to sing the anthem live on Fox News. Brown and Principal Trevor Putnam joined the students for their performance at the school Monday. Brown said her