Exploring the relationships between teacher education, teaching, and student achievement is a complex undertaking for a host of reasons, including the complexity of teaching, the number of different approaches to teacher education, the challenges associated with measuring teacher knowledge and teacher effectiveness, and the multiple mediators that operate in the study of teaching and learning. Teaching expertise requires technical skills that support instruction, theoretical knowledge, codified knowledge that guides professional decision-making, and critical analysis, which, in turn, informs the enlistment of technical skills and the development of codified knowledge. There is little consensus regarding the specific teacher characteristics that consistently lead to student achievement, although one hypothesis that has received considerable attention in the literature is the importance of teacher subject-matter knowledge. One of the challenges to making definitive statements regarding teacher education and its effects on teaching is that there are multiple approaches to teacher training. These approaches differ in terms of the candidates recruited, admission requirements, course content, the duration of training, the roles and extent of field-based experiences, and relationships with schools. Among claims regarding alternative preparation programs (i.e., programs that are not university-based), for which there is emerging support, is that alternative route teacher education programs are attracting a pool of prospective teachers of diverse age and ethnicity. Furthermore, alternatively certified teachers are choosing to teach in urban settings or settings with large numbers of minoritized students. With respect to measuring the effects of teacher education, a number of methods have been deployed including correlational studies investigating, for example, the relationship between the number of reading courses a teacher has taken and student performance on reading assessments, descriptive case studies of educational systems that are identified as successful, syllabus studies, and quasi-experimental studies. The field is developing more sophisticated and comprehensive measures and methods, as well as theoretical constructs to guide the study of teacher education and its effects on teaching and learning. The study of teacher education and its effects on student learning will benefit from the use of multiple methods—for example, large-scale studies complemented by carefully constructed case studies. In addition, this area will benefit from interdisciplinary scholarship by teams that include scholars who have a deep understanding of teaching and learning, adult development, school systems, and economics so that the field can acquire a more coherent and comprehensive understanding of the complexity of becoming a teacher.