This paper discusses an oral assessment intervention in environmental education at two tertiary institutions in South Africa. A qualitative study grounded in a social constructivist framework, the inquiry locates learning and assessment of environmental education based on practical activities and first-hand experience within the framework of situated learning, and explores processes of constructing and assessing knowledge within the learner's community of practice. The paper focuses on how communities of practice can be used as a possible learning approach in environmental education to address the diversity and challenges of classrooms, and on the efficacy of oral assessments structured to encourage thinking through dialog in such settings. (Contains 1 note.)