This study examines an assessment strategy used with incarcerated literacy learners. The strategy employed a traditional set of reading tests as well as open-ended interviews. Two stances--increasingly reconciled in the reading community--framed this assessment: (a) a post-positivist stance that promotes a normed, component-level assessment of reading; and (b) a social-constructivist one that attends to incarcerated learners' beliefs that anchor instruction. This framework respected the value commitments of each worldview. The study reports two sets of findings--about learners' reading patterns and beliefs--and then discusses two methods, pragmatic and dialectical, used to juxtapose and relate the findings across paradigms. Though time consuming, the study found this approach provided a way to (a) transcend normative-personal dualisms, (b) provide a check on over reliance of pet theories, and (c) cultivate a critical stance toward prison education. Due to length, the study is reported in two parts. Part I, presented here, includes the quantitative findings. [For Part II, "Performance and Beliefs: Two Assessments of Literacy Learners in Prison, Part II," see EJ1185222.]