It is generally theorized that English Language Learner (ELL) students do not succeed on state standardized tests because ELL students lack the cognitive academic language skills necessary to function on the large scale content assessments. The purpose of this dissertation was to test that theory. Through the use of quantitative methodology, ELL students' writing prompt response scores (Topic Development and Standard English Conventions) were compared to their English Language Arts (ELA) and Math scores on the Massachusetts Comprehensive Assessment System (MCAS). The specific questions that guided this research study were (a) Are ELL students' writing prompt response scores and MCAS scores related, (b) Is there a significant difference in the writing prompt response scores and MCAS scores of female and male students, and (c) To what extent does the years lived in Massachusetts affect the writing prompt response scores and MCAS scores? Data display included correlational matrix, scatterplots, boxplots, bar graphs, and histograms. Data analysis included statistical tests such as correlation, regression, comparison of means, t test for independent samples, and chi-square goodness of fit test. The study confirmed that higher English language proficiency scores had moderate positive correlation with higher standardized test scores in ELA and Math. The study also confirmed that the difference in the language proficiency scores of females and males, where females outperformed males, was statistically significant. The study did not confirm that increased number of years in Massachusetts contributed to increased language proficiency scores nor standardized test scores. The study also did not confirm that the difference in the higher language proficiency scores for female students and higher mathematics scores for male students was statistically significant. The dissertation recommends that (a) Massachusetts implement the ACCESS test for language proficiency determination as it is a better measure of academic English proficiency, (b) Districts use the data from ACCESS to provide teachers with professional development geared towards discovering best practices for raising ELL students' academic English proficiency, and (c) Replace Bthe MCAS test with PARCC test, which is closely aligned with ACCESS so that the test results will be valid and reliable as mandated by NCLB. [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.]