MOUNT VERNON — Dozens of choir students at Mount Vernon High School warmed up their voices Wednesday morning, changing pitch and enunciation as student teacher Brandon Waring listened and critiqued.Watching from the side of the classroom was the district’s first-year superintendent, Greg Batenhorst, crafting feedback of his own — for the teacher.“The only way that we as individuals grow, whether we’re superintendents, teachers, students, is just that constant feedback,” said Batenhorst, 55.