I think context-specific norms are important, too. I was on a lot of Little League teams where the coach was a curmudgeonly guy who was always yelling, and the kids mostly didn't mind being yelled at. It was happening to everybody, so it didn't mean anything bad about them personally. Same thing in school; some teachers were just mean. But then there were teachers who would treat different kids differently. Some kids would get the acid tongue over and over again no matter how hard they tried; others just got sweetness and light. That's terrible. It definitely doesn't have the desired effect; at least, I hope no teacher would want to make kids feel sick about coming to school every day.

If you establish a norm that everybody gets yelled at, even the better performers, then getting yelled at comes to just mean "pay attention" or "you need to focus more on this." Otherwise getting yelled at means, "You are not living up to the standards of the group, and we resent you for it. You should worry about what's going to happen to you here, if you're even allowed to remain."