K.P.
She just might not be comfortable using the potty at school yet. She is used to having mommy and daddy there, and your not when at school. Having to ask someone different to help her might be a little scary, and not what shes used to. At least she is doing well at home with it. I would keep her in the pull ups while she goes to school, and just keep encouraging her to ask the teacher when she has to go, and let the teacher know to keep up with asking her frequently. That way she is still trying, but if she has an accident then its okay. Shes still little, she will get there soon :)