We provide evidence on the effectiveness of a school-based program that uses a non-monetary penalty and regular monitoring to prevent risky behavior among adolescents in Indonesia. The field experiment invited students to sign a pledge to abstain from tobacco use and a similar pledge for parents to monitor their children. To test group incentives, a subset of treated schools also competed against each other for the highest tobacco abstinence rates. We find that the individual pledge increases biochemically verified tobacco abstinence by 5 percentage points. This effect is sustained 3 months after the program ended. School competition has no additional impact on tobacco abstinence. Our findings highlight the effectiveness of non-monetary incentives to curb risky behaviors among adolescents who face limited self-control and peer pressure.