Today, more than 60 percent of teachers in the United States work under a union contract. The rights of teachers to unionize and bargain together have expanded dramatically since the late 1950s, when states began passing "duty-to-bargain" (DTB) laws that required school districts to negotiate with teachers unions in good faith. Recently, though, states such as Wisconsin, Indiana, Michigan, and Tennessee have sought to weaken the ability of teachers unions to negotiate contracts in K-12 education. Advocates for these restrictions claim that unions have a negative effect on the quality of public education and, therefore, students' life chances. Those in favor of teacher collective bargaining, on the other hand, argue that unions make the education system more effective by empowering teachers who are in the classroom and by giving them a role in shaping their working conditions. Due to data limitations, however, empirical research has not credibly addressed the critical question of how teacher collective bargaining influences student outcomes. In this study, the authors present the first evidence on how laws that support teacher collective bargaining affect students' employment and earnings in adulthood. They do so by first examining how the outcomes of students educated in a given state changed after the state enacted a duty-to-bargain law, and then comparing those changes to what happened over the same time period in states that did not change their collective-bargaining policies.