Discussions about environmental and sustainability issues in classrooms can bring different political visions, opinions and conflicts to the fore. From a pluralistic perspective on environmental and sustainability education (ESE), such political differences and conflicts can be seen as a suitable starting point for teaching, rather than as an obstacle to overcome. But how can teachers approach this political dimension of ESE? This chapter outlines deliberation and agonism as two different approaches to the political dimension of ESE. With a deliberative approach, the role of rational and respectful communication is underscored as is the ideal to reach for consensus in classroom discussions. With an agonistic approach, the role of emotions, and how they are intertwined with political visions in sustainability issues, are highlighted. From an agonistic perspective, the teacher should not aim for a consensus in classroom discussions, but instead aim at enabling conflicts and pluralism to have a democratic outlet in discussions. A main point of this chapter is that deliberation and agonism should be seen as two different approaches to the political dimension in ESE, as they draw on different ideas about classrooms and conflicts and have different educational consequences.