Showing open dislike toward a student is transmitted to the class. These actions create animosity, as well as the possibility that students may try to live up to these expectations. Never punish the entire class for what one student has done. Help the class formulate class rules and regulations. Post these rules in the room and review them periodically.
Norms established by the group are more likely to be respected.
Don't look for miracles to happen overnight. If a student has a history of misbehavior and maladjustment over a period of years, nothing the teacher can do will change the student completely overnight. Don't be discouraged when, after a period of improvement, the student with problems suddenly regresses. Physical proximity is the best tool. Moving throughout the classroom is an excellent deterrent to misbehavior.