Answer/Sister Marilyn Arnold
My first reaction to this question is to ask another question: Are we, can we ever be, exempt from Church standards, whether in dress or behavior? Can we expect the Lord to bend his principles or put them aside for certain occasions? I think the answer has to be no to the general question, but there are some aspects of the specific question about marchers and cheerleaders that we need to examine. For example, does adherence to LDS standards mean a girl in a marching group has to wear a knee-length costume? Perhaps the answer to this question can also be suggested by another question: Should an LDS girl wear a knee-length bathing suit when she goes swimming or a turtleneck gown to a dance? Is a ballerina immodest if she performs in standard ballet attire? Modesty in dress is at least partly dependent upon the appropriateness of a particular costume to the occasion or activity for which it is worn. What is appropriate and modest for one activity may not be for another. We have to exercise judgment and make every effort to obey the spirit of the law.
A shorter-than-knee-length skirt can be appropriate for a marching group or for cheerleaders. But even so, the costume need not be immodest. In fact, a Latter-day Saint girl who is a member of such a group can be a strong voice in the choice of costumes. And she should speak up, insisting that the costume be in good taste, appropriate, and modest. Marchers and cheerleaders are in a very real sense on display. I am sure there is no relationship between the brevity of costume and the excellence of a performance. If her performing group, over her protests, selects an immodest (and hence, inappropriate) costume, a Latter-day Saint girl should most certainly choose in favor of the eternal principle.