This article reports on the development of online assessment tools for disengaged youth in flexible learning environments. Sociocultural theories of learning and assessment and Bourdieu's sociological concepts of capital and exchange were used to design a purpose-built content management system. This design experiment engaged participants in assessment that led to the exchange of self, peer and teacher judgements for credentialing. This collaborative approach required students and teachers to adapt and amend social networking practices for students to submit and judge their own and others' work using comments, ratings, keywords and tags. Students and teachers refined their evaluative expertise across contexts, and negotiated meanings and values of digital works, which gave rise to revised versions and emergent assessment criteria. By combining social networking tools with sociological models of capital, assessment activities related to students' digital productions were understood as valuations and judgements within an emergent, negotiable social field of exchange.