Data is the key to unlocking this mystery. Does your school allow for parental observation?
Even if not, no school can prevent a parent from observing outdoor play at recess from public property.
Some of the most valuable information I collected about my DS' former teacher's habits were gleaned from watching her oversee recess while unaware that I was watching. I should add that regional privacy laws may allow you to publicly film the teacher acting out, which provides irrefutable evidence in support of your case. (Just be sure you are on the side of right if you proceed with recording.)
Also, if you can get any answers in writing, that provides a nice record of the teacher's responses. Last year, I received a written, signed note from the teacher regarding IEPs that was in violation of our identification regulations. We opted out of that particular school, but it would have been a useful document to bring to advocacy discussions had we stayed.
