Kindergarten-second grade teachers often have to navigate conflicting paradigms as they attempt to honor the developmentally appropriate practices best suited for their young learners while working within the demands of the current educational paradigm of high-stakes testing and standardization. This challenge is acutely experienced in the assessment of young children, yet little research has been done to look at how teachers in the early elementary years approach or use assessment in developmentally appropriate ways. The purpose of this study was to use a constructivist grounded theory approach to address the overarching question: How do K-2 teachers come to their conceptualizations regarding developmentally appropriate practices and strong classroom assessment practices? Thirty-five teachers were interviewed in reaching theoretical saturation. Through the constant comparative process of data generation, data analysis, and extensive memoing, the researcher generated a theory with "I," "They," and "We" phases to explain the influences on teachers. The study also revealed how teachers conceptualize assessment and the ways teachers' knowledge, beliefs, and practices interact with each other in regard to classroom assessment and developmentally appropriate practice. The influences of school district administration, teaching colleagues, and experience through time were some of the most considerable influences. Among its implications, the theory suggests a need for more dissemination of knowledge of best practices in early elementary education. The theory also provides a framework for future research to improve assessment decisions and inferences in early elementary classrooms. [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.]