Personally I would find it hard not to take exception to the fact that my child could not go to the toilet when required and would be compelled to speak to the teacher about it. I would speak to DD first to establish if this was a one off or if she did need to go to the toilet quite often when in class. If she did I would explain to her about using the toilet during breaks so there is less disruption to the class and then speak to the teacher about strategies that can be used at school to prevent this happening as I do not find it acceptable that my daughter wets herself in class. If it was a one off I would say that I expect the teacher to know my daughter well enough that if she needs to go to the toilet she NEEDS to go to the toilet and again it isn't acceptable that she wets herself.

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The class is right for the other students, but is no longer right for her, therefore the best way to be fair to her is to move her to another class with more objective expectations. Be honest with her. Kids tend to have a sense of what is right and I'm sure she feels that something is off.

I too would be straight with her and explain the reasons why you think she should be moved. Give her examples of your concerns and openly discuss them with her. That way, maybe? she won't think she is being punished.