Source: Educational Researcher, 40 (6): 271-280. August/September 2011.
This article describes a study which explored the effectiveness's development of teachers in North Carolina public schools during their first five years in the classroom.
The authors contrasted the beginning teachers' effectiveness with the effectiveness of teachers who stayed with that of those who left.
It was found that across grade levels, teachers’ effectiveness increased significantly in their second year of teaching but flattened after three years.