With the national trend to link student achievement results with teacher evaluation ratings, it is critical for teachers to examine and interpret children's assessment results collaboratively. This study explored how the clinical interview process can be integrated into a professional learning experience to support teachers in identifying mathematical learning gaps and progressions, especially among diverse learners. In addressing the issue of "unconditional believing," clinical interviews can inform teachers of unseen attributes in their learners' thinking and uncover student potential. Through clinical interviews and discussions around open-ended tasks and student solutions, the study explored how teachers respond to evidence from results for their diverse learners. It also sought to identify how teachers' assessment practices are impacted by examining their student assessment work and related student interviews. The research was developed around an "Assessment Study" professional learning model in which three groups of teachers collaboratively examined and discussed two sets of student work on related mathematical tasks. One group completed pre/post surveys and participated in the "Assessment Study" with a clinical interview component involving eight students; the second completed pre/post surveys and participated in the "Assessment Study" with no clinical interviews; the third completed the pre/post surveys without participating in the "Assessment Study." The data included transcripts of teacher discussions, language from reflection sheets completed during professional learning sessions, student work, transcripts/videos from student interviews, and pre/post surveys for all three groups. The analysis of data found that both groups experienced uncertainty and confusion during the scoring process, while the clinical interview component enhanced all analyzed categories of discussions and reflections. Teachers who viewed clinical interviews gained greater interest in questioning their students further beyond their work, focused on student learning approaches (e.g., visual, verbal) and affective attributes, and experienced greater uncertainty than non-interview groups. It was recommended that teachers participate in an "Assessment Study" with a clinical interview component to gain insights into children's mathematical thinking and misconceptions. Policymakers are encouraged to consider linkages between student and teacher confusion related to the learning process and how a child-centered view of assessment can provide more insights than typical assessment scores. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]