One of the teacher's many challenging tasks is maintaining a positive classroom environment, and it is important to remember that both the teacher and the students are responsible for this. A teacher must take the lead, however, and perhaps the most important step to take as a teacher to maintain a positive classroom environment is to clearly define expectations for classroom behavior and reward good behavior. Try to come up with ways to reward students for doing well; a punitive system is very often the least effective system for dealing with difficult situations and student interactions.
Many teachers mistakenly believe that defining punishments for bad behavior will somehow help create and maintain a positive classroom environment. Students are far more likely, however, to change their behaviors for rewards than they are for fear of punishments. It is important to include the students in the rewards process and allow them to work toward something, rather than work against a punishment. The rewards structure does not have to be complex, but it should include activities or other rewards the students will be interested in. For example, if students hand in homework on time, they can have five to ten minutes at the end of class to perform an activity they enjoy.
A teacher is, of course, bound to lose his or her patience at some point, and this can be one of the most damaging occurrences that will prevent a positive classroom environment. The teacher must remember that he or she is an important part of that positive classroom environment, so if the teacher gets to the point of frustration and anger, the teacher should step out of the room and remove him or herself from the situation momentarily. If the problem is with a particular student, have that student leave the room with you. Yelling at a student or otherwise addressing bad behavior in front of other students can lead to a worsening situation quickly. One on one interaction with the student is preferable instead. If punishments need to be doled out, do not do so in front of the entire class.
The most important thing a teacher must do to maintain a positive classroom environment is to hold himself or herself to the same standards as the students. The students are extremely likely to notice a teacher's behavior, both positive and negative, and the old retort, "because I said so" will make the teacher lose credibility quickly. If the teacher expects students to be on time for class, for example, the teacher should be on time and ready to teach the moment the bell rings.