Even though sustainable development concerns a common future "for all," cultural diversity is often absent from teaching and educational policy documents on education for sustainable development in Norway. We present a dialogue sequence from a science class. The empirical material originates from a nine-month ethnographic classroom study in an upper secondary urban classroom in Norway. Our aim is to provide awareness of how plurality and diversity aspects of a sustainable future might widen pedagogical approaches to education. We used critical thematic analysis, theories of "dialogic space" and the concept of "othering" to examine the dialogue. In the dialogue sequence, the students used their own life experiences, representing different backgrounds, to give personal voice to three kinds of groups: we as citizens in the Norwegian welfare state, we with personal primary experiences from outside Norway and "we" as 'foreigners' in the gaze of others. During the conversation, the focus moved from "others as needing assistance and as a burden" towards "common responsibility." Social and economic issues, comprising the local and the global, were addressed through personal narratives. The students started the conversation from a "reformative" approach on sustainable development, which seems to be in line with Norwegian school policy and practice on the topic. From that perspective they emphasised the need for knowledge and information as an important part of a sustainable future. During the conversation, the focus shifted, it's as if they began to doubt.