Remain calm when a student has an outburst in your classroom. Taking a few deep breaths and gaining your composure can work wonders for the management of your class. Keep your voice low and your movements slow and gentle as you talk to the student and attempt to help her resolve the issue. You will find most outbursts can be diffused this way.
Students who lack appropriate coping skills may have a more difficult time than other students dealing with frustration and anger or calming themselves when they get upset. Teach these students coping mechanisms such as counting to 10 before speaking to avoid a verbal outburst. If the moment still hasn't passed, the child can be taught to say what he is feeling in an appropriate, non-threatening way. Children can be taught deep breathing exercises or given a stress ball to squeeze in their desks to reduce frustration. Being able to come to the teacher to talk at the beginning of the day can help students who may bring stressors from home that affect their school day.
Be proactive and know your students. You may not always be able to prevent an outburst or a frustrated or angry moment but knowing your students can go a long way in identifying their emotional triggers and the best way to quickly calm them. There will be less disruption to the rest of your class, as well. Have a separate area, a small tent or rocking chair in the corner of the classroom, where students can go to calm themselves down. This should be a voluntary decision, not a punishment.
Avoid dwelling on the negative when trying to calm a student. Use encouraging words and praise her accomplishments. If you must point out something negative about her classwork, start with a positive remark first. For example, "I like the story you told. It's very interesting. Please return to your seat and make sure you have capital letters at the beginning of all your sentences." This alone can go a long way to helping a student resist acting out and become more positive herself.
When pointing a child's behavioral issues, acknowledge the feeling and what he did wrong, then place the responsibility on his shoulders. "I understand you are angry that time ran out, and it can be frustrating when you don't get a turn. It's okay to feel angry and frustrated but you may not yell and scream in this classroom. What can you do instead?" Make a list he can refer to of appropriate ways to calm himself should the need arise again. This will help him increase his frustration tolerance and solve problems for himself.