In education, assessment helps shape teaching practices and student outcomes, as it influences how teachers perceive their roles, approach instruction, and engage with students. This study investigated 3rd-8th grade English Language Arts and mathematics teachers' conceptions of the NWEA MAP Growth assessment, focusing on four key factors: (1) improvement for teaching and learning, (2) school accountability, (3) student accountability, and (4) assessment irrelevance. The research examined the relationship between teachers' conceptions and variables such as grade levels, content areas, and students' academic growth as measured by NWEA MAP scores. Using a descriptive correlational design, data were collected from 61 teachers within a South Texas K-12 public school district predominantly serving economically disadvantaged students. Teachers completed the "Teachers' Conceptions of Assessment abridged" survey ("TCoA-IIIa"), and student growth data were analyzed for correlations with teachers' conceptions. The findings revealed significant differences in teachers' conceptions based on grade levels and content areas. Elementary teachers generally reported more positive views of the NWEA MAP, particularly in its utility for improving teaching and learning and holding schools and students accountable. In contrast, secondary teachers were more likely to view the assessment as irrelevant. Among content areas, mathematics teachers reported less favorable conceptions across most factors. Despite these observed differences in teachers' beliefs, the study found no significant correlations between teachers' conceptions and their students' academic growth. This suggests that factors other than teachers' assessment conceptions may have a more substantial impact on student outcomes. The results highlight the complexity of teachers' beliefs about assessment and suggest that while understanding these conceptions is important, additional strategies may be necessary to enhance student achievement. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]