In recent decades, the Commonwealth of Massachusetts has implemented reforms aimed at improving and controlling the quality of the teaching workforce in public schools. Among those reforms are tests for licensure that assess both general and content-area specific knowledge, requirements for ongoing teacher professional development, and procedures for teacher evaluation. Notable is the continued high performance of Massachusetts's commonwealth charter schools--schools that, by law, do not have to comply with requirements for teacher licensure. With a teaching workforce that is comparatively young, unlicensed, and slightly less likely to stay in the profession, Massachusetts's charter schools achieve stellar student achievement results. Evidence presented in this report from case studies of five high-performing charters schools from around the state reveal that these schools create highly effective teaching workforces in specific ways. The schools included in this report have varied but well defined philosophies about the importance of teacher retention and the need to build organizational pipelines to support the induction of new teacher recruits and the growth of more experienced faculty members.