The study examined the self-reported understandings of selected 3rd to 12th grade teachers had of assessment and the assessment practices they reported implementing in their classrooms along with evidence extracted from written lesson plans. The literature on classroom assessment supports the idea that teachers who create meaningful assessments, offer corrective action, and give students multiple opportunities to demonstrate success can improve their instruction and increase student learning (Guskey, 2003). McMillan, Myran, and Workman (2002) argued that teachers' understanding of assessment matters are inadequate; although there is common use of standardized math and reading tests, there is limited knowledge of how the assessments are scored, what inferences can be drawn, and even less knowledge of issues involving reliability and validity. The mixed-method study examines the relationship between these two phenomena using a model of assessment literacy that holds the student as the most essential variable in a data-driven practice involving interdependent actions that results in increase achievement. To achieve this goal, a teacher questionnaire was distributed to teachers working in 10 different schools serving varied student populations. As a method of triangulation, the data gathered by the questionnaire was reconciled with a systematic analysis of lesson plans to establish consistent themes. Findings indicate an implementation gap as it relates to teachers' surface knowledge of assessment and what they practice daily in the classroom. Additionally, the study found that teachers do not consistently integrate assessment activities into daily instruction. [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/en-US/products/dissertations/individuals.shtml.]