The current teacher workforce is younger, less experienced, more likely to turnover, and more diverse in preparation experiences than the workforce of two decades ago. Research shows that inexperienced teachers are less effective, but we know little about the effectiveness of teachers with different types of preparation. In this study, we classify North Carolina public school teachers into "portals"--fixed and mutually exclusive categories that capture teachers' formal preparation and qualifications upon first entering the profession--and estimate the adjusted average test score gains of students taught by teachers from each portal. Compared with undergraduate-prepared teachers from in-state public universities, (a) out-of-state undergraduate-prepared teachers are less effective in elementary grades and high school, (b) alternative entry teachers are less effective in high school, and (c) Teach For America corps members are more effective in STEM subjects and secondary grades.