I study how teachers’ assigned job tasks—the practices they are asked to use in the classroom—affect the returns to math skills in teacher productivity. The results demonstrate the importance of distinguishing between workers’ skills and job tasks. I examine a randomized trial of different approaches to teaching math, each codified in a set of day-to-day tasks. Teachers were tested to measure their math skills. Teacher productivity—measured by student test scores—is increasing in math skills when teachers use conventional “direct instruction”: explaining and modeling rules and procedures. The relationship is weaker, perhaps negative, for newer “student-led” methods.