Have well defined consequences

Set specific consequences for breaking the rules. Decide what those consequences are and then implement them consistently. Your consequences should follow a procedure that starts with a non-verbal signal (such as just looking at the student), to a verbal signal (asking the student to please stop talking), to a verbal warning (if this continues there will be consequences), to the implementation of the consequence. The consequences are up to you and depend on the program of the school. Many schools have a detention system (students do despise detentions), or perhaps writing lines, or sitting away from other students.