Don't retaliate toward an angry parent with more anger or defensiveness. Make the parents understand you know how they are feeling and that you respect their feelings. Say things like: "I can understand how that's frustrating," or "If I were you, I'd be angry too." Demonstrating empathy will help the parent move from a hostile stance toward a cooperative one. Demonstrating empathy will help the parent to see and even empathize with your side of things.
Try saying something funny and lighthearted. Tell a funny anecdote about a time you found yourself in a similar situation. Mention a positive but humorous aspect of the child's personality. Humor, like empathy, helps reduce defensiveness. Humor is such an effective tool for diffusing emotion that police officers often use it to keep themselves calm, and others cooperative. Be sensitive when using humor, however. The parent may take your remark the wrong way, so choose your words carefully.
Now that you've demonstrated that you understand the parent's concerns, voice your own. If the angry parent's child is disruptive in class, emphasize your responsibility to maintain a high standard of safety and education for all students. Use language that is firm but not inflammatory. Calmly state your responsibility, and propose two or three possible courses of action. Engage in open dialogue with the parent and try to reach an amicable decision. If you cannot reach a joint decision, simply inform the parent what course of action you will take and politely end the conversation.
Execute the plan of action and keep in touch with the parent until the issue is completely resolved. Successful relationships depend on following through with your promises. In the school setting, everyone who is involved with the education of a child should have strong relationships with one another and with the young person.