Can well-being be taught at a large scale, and should it be taught in schools? Does teaching well-being improve academic performance? In Study 1, 18 secondary schools (n=8,385 students) in Bhutan were randomly assigned to a treatment group (k=11) or a control group (k=7). The treatment schools received an intervention targeting ten non-academic well-being skills. Study 2 was a replication study at a larger scale in 70 secondary schools (m = 68,762 students) in Mexico. The schools were randomly assigned to a treatment group (j = 35) or a control group (j = 35). Study 3 was the last replication study at a larger scale in 694 secondary schools (q = 694,153 students) in Peru. The schools were randomly assigned to a treatment group (h = 347) or a control group (h = 347). In all three studies, students in the intervention schools reported significantly higher well-being and they performed significantly better on standardized national exams at the end of a 15-month intervention. In Study 1, the results for both well-being and academic performance remained significant 12 months after the intervention ended. For Studies 2 and 3, time will tell if our results endure 12 months after the end of the intervention. In all three studies, perseverance, engagement, and quality of relationships emerged as the strongest mechanisms underlying increases in well-being and enhanced academic performance. Our results suggest that, independent of social, economic, or cultural contexts, teaching well-being in schools on a large scale is both feasible and desirable.