An increasing share of new teachers enter the profession through alternative certification programs. While these programs increase teacher supply in areas facing critical shortages, they also increase instability in local teacher labor markets via high teacher turnover. A fundamental question is what effect these programs have on student achievement over the long run. To address this question, I study Teach For America (TFA) teachers working in New York City (NYC) between 2012 and 2019. This research brief reports on three key findings. First, I document five-year cumulative retention rates and find that, as expected, retention is lower for TFA teachers (25%) than for other NYC teachers working in similar schools (43%). Second, I estimate within-teacher returns to experience using a teacher fixed effects strategy and find that TFA teachers who continue teaching through year five improve at double the rate of the average NYC teacher. Third, I model the joint relationship between turnover and performance over time and find that the TFA performance advantage is large enough to offset turnover costs. I conclude that the net effect of TFA hiring on student achievement is positive in the short and long run.