This study addresses two questions related to teacher preparation and certification: (1) What are the relative effects on student achievement of teachers who chose to be trained through different routes to certification and how do observed teacher practices vary by chosen route to certification?; and (2) What aspects of certification programs (such as the amount of coursework, the timing of coursework relative to being the lead teacher in the classroom, the core coursework content) are associated with teacher effectiveness? In 63 study schools, every grade that contained at least one eligible alternatively certified (AC) and one eligible traditionally certified (TC) teacher was included. Students in these study grades were randomly assigned to be in the class of an AC or a TC teacher. Students were tested at the beginning of the school year as a baseline measure and at the end of the year as an outcome. Classroom instruction was observed at one point during the year as an outcome. Reported findings include: (1) Both the AC and the TC programs with teachers in the study were diverse in the total instruction they required for their candidates; (2) While teachers trained in TC programs receive all their instruction (and participate in student teaching) prior to becoming regular full-time teachers, AC teachers do not necessarily begin teaching without having received any formal instruction; (3) There were no statistically significant differences between the AC and TC teachers in this study in their average scores on college entrance exams, the selectivity of the college that awarded their bachelor's degree, or their level of educational attainment; (4) There was no statistically significant difference in performance between students of AC teachers and those of TC teachers; (5) There is no evidence from this study that greater levels of teacher training coursework were associated with the effectiveness of AC teachers in the classroom; and (6) There is no evidence that the content of coursework is correlated with teacher effectiveness. Supplementary Technical Information on Data Collection, Response Rates, and Analyses is appended. (Contains 90 footnotes and 28 exhibits.)