You have to identify the specific issue we're enraged over because when it is implied instead of explicitly stated the recipient can rationalize you're bothered by something else.
Also, she's not the person to direct this to. The Super and higher are who should be receiving these letters because they can force the Principal to withdraw the order keeping the mom off the property and to even apologize. We have to use the very words that have been attributed to the Principal whenever possible so that her very words that she order the prohibition because of a legally acquired carry permit are the focus of our concern.