Establishing rules in the classroom around respect can be much more effective if the students put the rules in place themselves. Take half a day at the beginning of the school year to make a class constitution together. Have a general discussion about what principles it should include, including the right to hold your own opinion, to communicate it freely and not to be shot down or belittled by others. Break the class into small groups to come up with specific rights and responsibilities that all members of the class can agree on.
Part of learning to respect the opinions of others is recognizing that we all come at issues from different perspectives. Organize a day where students come to school and teach the rest of the class about their cultural background. Let students ask questions to see how different they all are. Engage the class in a discussion about our similarities, even though we come from different places. You can have students write a paragraph or two about what they learned from others, and why they think some people might have different opinions than they do.
Drama games and activities are a useful way to teach students about respecting others' opinions. Come up with a number of situations, such as two people arguing about what movie to see. Write them on slips of paper. Have two students come to the front of the room and choose a scenario at random. Have them act out the situation and the argument. Ask the rest of the class for suggestions on how the disagreement might be resolved, and have the students improvise different resolutions. Repeat the activity with different students and a new scenario.
Students should learn from an early age that it is possible to hold conflicting opinions at once. Learning this will help them respect opinions that others hold. Give your students a topic that is relevant to them, such as cellphones in the classroom or school uniforms. Have your students write two pieces on the issue, one for and one against. Once they have done this, have a group discussion about what they learned from trying to see opposite sides of the same issue.