Efforts to increase the quality of the teacher workforce by weakening and repealing tenure laws and collective bargaining rights have gained considerable momentum in recent years. Despite the growing number of states that have adopted these reforms, we know very little about how they may strengthen or undercut teacher quality. This proposal will examine the fundamental question: How does weakening or eliminating tenure protections and collective bargaining rights affect teacher labor markets and student achievement? The PI will examine this question by exploiting differences in the timing and occurrence of state policy reforms from 1990 to 2015 to estimate the causal impact of five well-defined policies: 1) repealing tenure, 2) extending the number of probationary years prior to being eligible for tenure, 3) considering teacher performance in tenure decisions, 4) repealing collective bargaining rights, and 5) eliminating mandatory union dues. This research will, for the first time, provide evidence on how these policy changes affect who chooses to enter the teaching profession as well as how much effort teachers invest on the job (as measured by hours worked and days absent). We will also provide new evidence of the effect of these reforms on student achievement and dropout rates.