At least 79 teacher assistants and instructors at the University of North Carolina-Chapel Hill are threatening to withhold grades unless their demands in the Silent Sam controversy are met, local activists say. A proposal by the universitys Board of Trustees to rehouse Silent Sam in a $5.3 million historical center has been met with protests from students and community activists, but a proposed strike crosses a line, UNC System Board of Governors member Marty Kotis told Carolina Journal.