The purpose of this study was to examine the relationship between school climate and academic achievement in English language arts and mathematics in third through eighth grade students in Illinois. This study employed a complex correlational design utilizing multiple regression analysis. Secondary data came from the Illinois School Report Card data file. The study compared academic achievement as measured by the Partnership of Assessment of Readiness for College and Career (PARCC) for 2016-17 and 2017-18 with school climate as measured by the 5Essentials Survey while controlling for the effects of school-level socioeconomic and race variables. The results of the study show that school climate has a significant positive relationship to academic achievement, even when controlling for school demographics. In addition, school climate is a significant predictor of academic achievement. Holding school demographics constant, for every one standard deviation unit increase in overall 5Essentials scores, there was an increase of approximately one-fifth to one quarter of a standard deviation unit in PARCC performance. The study also found that almost all essential supports identified in the 5Essentials Framework, Effective Leaders, Collaborative Teachers, Ambitious Instruction, Supportive Environment, and Involved Families, had statistically significant and positive relationships to PARCC performance. In addition, all essential supports were predictive of performance on the PARCC, with increases ranging from one-tenth to nearly one half standard deviation units for every standard deviation unit increase in Essential scores. The study found that Effective Leaders Essential scores were the least predictive of PARCC performance while Involved Families Essential scores were the most predictive. [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.]