If the windchill creates below zero effects, the kids stay inside for recess and lunch breaks. The district where I work has support staffing for the younger kids. Even my sons' district does. I have had days where they've come home with shoes untied, not many, but enough to stand out in my mind. Even when double knotted. Not just my son that has occupational therapy.
I'm actually angry for you with this teacher's knitpicking, to be honest. Instead of calling you in for a conference or making a phone call, he has sent home a note? It's this hanging your daughter's 'hangup' over you as though it defines you a total parent that's unnerving. She's 7. She'll outgrow this.