The value of social and emotional skills is increasing in the labor market, but we have limited knowledge on how education systems can foster these skills at scale. We present evidence from a large-scale field experiment in Norway testing an online curriculum fostering students’ capacity to take on new challenges, solve hard problems and learn new tasks. The Norwegian high school system has a choice architecture particularly conducive to studying challenge-seeking, as students make annual choices about the rigor of math classes and these choices are consequential for future higher educational opportunities. We find that the intervention increases the likelihood that students take a more challenging educational path. The treatment has a positive impact on students’ choices of advanced and more challenging math classes throughout all three years of high school. One concern is that taking more rigorous math courses can be detrimental for marginal students, reducing grade-point averages and even on-time graduation. We find no support for this concern.