In many school districts the policies that regulate personnel are governed by collective bargaining agreements (CBAs) negotiated between teachers' unions and school boards. While there is significant policy attention and, in some cases, legislative action that has affected the scope of these agreements, there is relatively little research that assesses how CBAs vary over time, or whether they change in response to states' legislative reforms. In this paper we compare CBAs in three states at two points in time: before and after substantial reforms in Michigan and Washington impacting collective bargaining and in California where there were no major statutory changes affecting CBAs. We find that few district characteristics predict changes in CBA restrictiveness over time, other than institutional spillovers from local bargaining structures. However, we observe that reforms to the scope of bargaining in Michigan and Washington drastically reduced the restrictiveness of Michigan and Washington CBAs relative to California.