This usually requires you to really listen to your child. As the mother finds out, the problem isn't the teacher, it is that her daughter still feels sad about things she lost in the disaster, including the pens she needed to do her homework. This mother took the time to ask her daughter questions and to discover the real cause of her daughter's frustration. By asking questions and listening, you give your child permission to tell you what is really wrong. Compare this response to how you talk to a spouse or a friend.
Parents can do that for children, too.
When children are stressed, they may hit their siblings, kick the dog, or do other aggressive things. While you need to make it clear these are not acceptable behaviors in any circumstances, you can still accept the feelings and give your children permission to cry, yell, or get out their sadness or anger another way. Let's go outside and run until we're not mad anymore. Share with your spouse or children what happened, how you felt, and what you wish had happened. Being honest sometimes means admitting that you don't know the answers to everything.