No recent reform has had so profound an effect as no-excuses schools in increasing the achievement of low-income black and Hispanic students. In the past decade, no-excuses schools—whose practices include extended instructional time, data-driven instruction, ongoing professional development, and a highly structured disciplinary system—have emerged as one of the most influential urban school-reform models. Yet almost no research has been conducted on the everyday experiences of students and teachers inside these schools. Drawing from 18 months of ethnographic fieldwork inside one no-excuses school and interviews with 92 school administrators, teachers, and students, I argue that even in a school promoting social mobility, teachers still reinforce class-based skills and behaviors. Because of these schools’ emphasis on order as a prerequisite to raising test scores, teachers stress behaviors that undermine success for middle-class children. As a consequence, these schools develop worker-learners—children who monitor themselves, hold back their opinions, and defer to authority—rather than lifelong learners. I discuss the implications of these findings for market-based educational reform, inequality, and research on noncognitive skills.