CENTER OF THE STAGE at Ann Arbor's annual Community Christmas Sing, scheduled to be held at 4:15 Sunday afternoon in Hill Auditorium, is reserved for Ann Arbor High School's a capella choir, pictured above as Miss. Juva N. Higbee, head of the public schools' music department, directs practice in singing carols. The choir will be part of a chorus composed of other students from the high school, and of students from St. Thomas school, University High School, and Jones, Tappan and Slauson Junior High Schools. Main job of the chorus will be to lead the audience in singing Christmas carols.