Myrna Shure: The first thing you want to do is rule out medical causes. Once that is ruled out, and assuming the child is old enough to have been potty trained, you might ask the parents if this happens at home. Try to find out if the parents know of particular anxieties the child may be experiencing, or whether she may simply be distracted easily, and not aware of her own body cues when she has to go to the bathroom.
You might try bringing a parent and the child together in private, and in a warm, caring, and supportive voice ask, “Is something bothering you?” If she doesn’t answer, try asking, “How do you feel about letting the teacher know when you have to go to the bathroom?” If necessary, ask, “Do you feel afraid to let her know?” If the child is old enough, you can add, “Do you feel embarrassed?” If she indicates yes, let her know that it is ok for her to let you know.
It is possible that the child feels angry, and this is her way of controlling what she perceives as controlling adults. By asking “Is something bothering you,” the child may reveal thoughts and feelings you are unaware of. Then ask her for her ideas on how to solve this problem. This may help this child feel empowered, and is more likely to respond because she is coming up with her way to deal with her discomfort.
If selective muteness is a problem at other times as well, then I suspect this is her way of controlling adults. Letting her express her thoughts and feelings will be helpful in this case. I have found that as early as age 4 or 5, children are capable of participating in this kind of dialogue.