In this study of novice teachers in North Carolina public schools, the authors investigated the development of teachers' effectiveness during their first five years in the classroom and contrasted the effectiveness of teachers who stayed with that of those who left. Across grade levels, teachers' effectiveness increased significantly in their second year of teaching but flattened after three years. The teachers who left the profession were less effective, on average, than those who stayed at least five years, but this finding is somewhat less consistent than the findings of an initial jump in effectiveness and diminishing returns to on-the-job development.
Henry, G. T., Bastian, K. C., & Fortner, C. K. (2011). Stayers and leavers: Early-career teacher effectiveness and attrition. Educational Researcher, 40(6), 271-280. https://publicpolicy.unc.edu/files/2015/07/Stayers-and-Leavers-Early-Career-Teacher-Effectiveness-and-Attrition.pdf