This study examines foster child case records to understand how intelligence testing was used by guidance counsellors and social workers to negotiate welfare resources with poor youths in the early twentieth century. Psychological testing justified racial hierarchy in a scientific language suited for a rational professional bureaucracy. Yet, it was also a technique for individual analysis that allowed poor children and youths to observe themselves and to speak about themselves in ways that countered biological determinism. The clinical reports and case notes suggest that foster youths often figured themselves as social actors resisting the unfavourable assessments presented by the professionals. The practice of making bio-social predictions about fostered youths, ironically, cleared space for an opposing figure to take shape in the recorded words of the youths: the agentive, political youth demanding recognition and resources. This article opens a rare window upon the "governmentality" of childhood by allowing us to consider the ways in which structures of assessment allowed the subject to view the self as an object. (Contains 5 tables and 46 footnotes.)