Purpose: The purpose of this study was to determine the extent to which third grade English reading achievement scores, as measured by the Texas English Language Proficiency Assessment System (TELPAS), differed between two groups of students--those educated in transitional bilingual classrooms taught by native-English speaking teachers (NESTs) and those educated in transitional bilingual classrooms taught by nonnative English-speaking teachers (NNESTs). A second purpose was to determine the extent to which third grade Spanish reading achievement scores, as measured by the Texas Assessment of Knowledge and Skills (TAKS), differed between two groups of students--those educated in transitional bilingual classrooms taught by native English-speaking teachers and those educated in transitional bilingual classrooms taught by nonnative English-speaking teachers. Methodology: ANCOVA was used to analyze data for each of the two research questions in my study. Participants were selected using purposive sampling from 31 elementary schools in a large urban school district in Texas. Findings and Conclusions: Findings from question one in my study established that the teacher's native language was not a significant variable in impacting students' scores on the TELPAS reading. Findings from question two in my study established that the teacher's native language was not a significant variable in impacting students' scores on the TAKS Spanish reading. [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.]