We provide empirical evidence of immigrants' specialization in skill acquisition well before entering the US labor market. Nationally representative datasets enable studying the academic trajectories of immigrant children, with a focus on high-school course-taking patterns and college major choice. Immigrant children accumulate skills in ways that reinforce comparative advantages in nonlanguage intensive skills such as mathematics and science, and this contributes to their growing numbers in science, technology, engineering, and math (STEM) careers. These results are compatible with well-established models of skill formation that emphasize dynamic complementarities of investments in learning.