Lateness....

[Crayola kiddies]

I would post a note on your door saying "all drop offs must be before xxxx (time) as we walk (child's name) to school and won't return until xxx (time). Anyone not here by xxxx must wait till I return". Make the leaving time on the note 10 mins before your actual leaving time as you will get parents pushing the envelope and arriving right at the time you need to leave and making it all the more hectic. And then yes leave when you need to leave and anyone arriving while you are gone must wait as they have been warned