The number of English Learners (EL) enrolled in general education classroom environments in Illinois is increasing. State assessment data demonstrates that EL students are academically behind in reading. Since general education teachers in Illinois are not required to have an ESL endorsement and teacher preparation programs do not consistently require ESL coursework, many EL students receive instruction from general education teachers who are not trained to assess or instruct EL students in a way that will meet their needs or begin to close the achievement gap. This quantitative causal comparative study aimed to determine if school districts should invest financial resources in endorsement coursework for general education teachers as a strategy for improving EL students' reading growth. The research focused on the Measures of Academic Progress (MAP) reading scores of fourth grade EL students. Using fall and spring assessment results, fourth grade EL students reading RIT, Lexile, and Vocabulary RIT growth data were compared to analyze the difference between students who were taught by an ESL endorsed or non-ESL endorsed general education teacher. The theoretical foundation for this study is Vygotsky's sociocultural theory, as it has been identified as a foundation for ESL endorsement coursework. The participants in this study were 12 fourth-grade licensed teachers from a suburb of Chicago, Il, and the 80 students on their class lists who have been identified as needing English language support. Of the 12, four teachers have earned an ESL endorsement, and eight have not earned an ESL endorsement. The findings indicated that fourth grade EL students' overall reading RIT and Lexile growth was significantly impacted when taught by an ESL endorsed teacher, but the ESL endorsement did not significantly impact fourth grade EL students' vocabulary RIT growth. [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.]