My 4-year-old doesn't tell when she has an accident :(

Lisichka

My 4-year-old daughter has been potty trained since she was 2. She's been pretty good, but occasionally has accidents at school (and at home). At school, it's usually during naptime and she just puts on her pants/tights over her wet undies and doesn't tell her teacher. At home, she sometimes gets distracted with playing and doesn't tell us. We make sure (as do the teachers at school) not to reprimand or punish for accidents, but at this point, what the heck can we do to make sure she at least tells her teacher/us. My only guess is that maybe she was reprimanded at some point for an accident at school and she's now scared to tell her teacher. I spoke with the school director and he says that they do not reprimand her for accidents, but do for not telling the teacher. Ugh, I thought this whole thing was over, but guess not :-/