Preschool coming up, what red flags/green flags to look for?

My son will be entering preschool early next month.I am wondering what red flags and green flags should I be looking for if any? I obviously can tell in some ways, but in many ways I can't because I don't know what's really the "norm" of preschool. via /r/Parenting http://ift.tt/2gOCXKp