It is widely acknowledged that charter schools tend to have less experienced teachers and higher teacher turnover, but to date, little effort has been made to identify the contribution of faculty experience and retention to overall charter effectiveness. I do so using a twelve-year panel of charter and mainstream student achievement in North Carolina, focusing on the state's middle schools. Indeed, new charter schools had twice the rate of new teachers as new mainstream schools, as well as lower rates of faculty retention. Consistent with past research, I find significant returns to charter school age in terms of math and reading achievement, and I rule out the possibility that charter maturation was driven by higher-achieving students selecting into older schools. Faculty development explains, at best, a small share of the observed maturation over the initial years of charter schools' operation. Charters of all ages were relatively ineffective at improving math achievement, but were on par with mainstream schools at improving reading achievement by their sixth year of operation. (Contains 5 figures and 7 tables.)