My daughter comes back with a rash from school every time

She only stays at the school for 2 hour and a half for her special program. Every time she waits to poop at school she comes back with a rash. Really bad rash. Does anyone here deals with the same situation? Do you just use diaper ointments with every change? How do I help prevent this? I don’t want to say something to the teacher and be rude, I’m sure they are busy. But it’s getting so frustrating.