These full year choir classes emphasize choral singing, music theory, listening, and performance. Ninth, tenth, eleventh, and twelfth grade students will comprise various classes according to achievement levels checked by audition. The classes may be composed of all males, all females, or mixed according to number and distribution of voices available. The names of these groups differ with the high schools in which they are organized and may participate in UIL competition. Students may be required to attend rehearsals outside regular school hours.