Aware of the challenges set before the Houston Independent school District by rapid growth in the numbers of English learner students, and a critical shortage of teachers with bilingual certification for more than a decade, members of Regional Educational Laboratory Southwest's English Learners Research Alliance sought information that districts can use when recruiting teachers and assigning them to schools and classrooms that serve large numbers of English learner students. To respond to this need, this study examined the relationships between teacher certification and growth in math and reading achievement and English proficiency among English learner students using data from the Houston Independent School District and the Texas Education Agency. The study assessed whether a teacher's certification type--bilingual or English as a second language--and certification route--additional exam (adding a certification area to an existing classroom teaching certificate by completing an exam), alternative (receiving certification through a nontraditional route that allows one to teach while completing the requirements), postbaccalaureate (completing a university program offered to people with a bachelor's degree or higher), or traditional (obtaining a bachelor's degree in education from an accredited university)--were correlated with growth in math achievement, reading achievement, and English proficiency (as measured by the most recent Texas state standardized exams) among English learner students whose home language is Spanish. Key findings from the main analysis are detailed and analyzed. Stakeholders may find the results of the study useful for understanding the teacher factors related to English learner student achievement, assigning teachers to English learner student classrooms at the school level, recruiting teachers at the school or district level, and developing standards for teachers of English learner students at the state level.