Positions for principals at one high school and two middle schools in Forsyth County were filled this week after they were left open by transfers to other schools and retirements. Karl Mercer, current director of accountability for the district’s central administration, will be the next principal at West Forsyth High School, according to personnel appointments approved in a Board of Education executive session Tuesday. “We are excited to have dedicated, veteran leaders in our district step into these three principalships,” Forsyth County Schools Superintendent Jeff Bearden said.