J.S.
I would talk to the director--but put your anger and frustration aside....and instead of expressing your displeasure with the teacher (which is probably 100% justified), ask the director what you can do to help your son be successful with potty training. Make it like you want to do everything you can to be helpful, and you aren't sure how to make him more successful at school. Maybe play just a little dumb, and show the director one of the potty sheets and ask her to help you interpret it--have her show you how often he was on the potty, when the accident happened, etc--and ask if maybe he could be encouraged to go the potty a little more frequently. Maybe the director will recognize that the teacher needs a little more training. I just know (from my job, and from my mommy experience) that anger/demands definitely have their place, but generally you really do catch more flies with honey than vinegar (is that how that goes) Try the sweet and innocent approach--if that doesn't work, you might need to be a little more forceful.