Studies have shown that teachers' beliefs influence their assessment practices. However, the overarching framework of those beliefs in relation to teachers' classroom assessment confidence has been largely unexamined. This research explored teachers' conceptions of assessment and their confidence regarding the implementation of sound classroom assessment practices. The Teachers' Conceptions of Assessment-III Abridged (TCoA-IIIa) and the Classroom Assessment Confidence Questionnaire (CACQ) provided quantitative data from 160 Kindergarten through 12th-grade teachers in three public school districts in the northeastern United States. Descriptive results revealed that teachers' collective self-perceived agreement was greatest for the student accountability purpose of assessment. Additionally, regarding classroom assessment confidence, participants rated themselves highest in effective communication of results. A Pearson correlation analysis between and among the four TCOA-IIIa and the five CACQ factors yielded 27 significant relationships. A factorial multivariate analysis of variance revealed a significant multivariate effect for type of assessment training. Further analysis of the data suggested the need to provide teachers with opportunities to collaborate with colleagues, reflect on their conceptions, and increase assessment literacy to improve student involvement in assessment. [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.]