moms of school age kids

How long do you wait to say something if your kid is being bullied? What do you feel is the difference between bullying and kids being kids? Who do you say something to first, the school? the parents? The teacher? And what exactly do you tell your kid (kindergarten in my case) to ignore it? To say crap back to the kid(s)? Hard to see your kid so heart broken and not want to go to school😠