For the better part of the 21st century, the idea that between 40 and 50 percent of teachers leave the profession within their first five years has been repeated within and outside of education and policymaking circles. But new research from the National Center for Education Statistics (NCES) suggests that those numbers are too high.

NCES found that ten percent of teachers who started a teaching career in 2007-2008 left teaching after their first year, but five years into their careers, 83 percent were still teaching. The study also suggests that new teachers who work under the guidance of a mentor are more likely to stay in the classroom than those who are not assigned mentors.

The old attrition figures come from studies conducted by the University of Pennsylvania’s Richard Ingersoll, a preeminent scholar on teacher attrition and the teacher workforce. Ingersoll says the statistics were a “crude approximation” he made in the absence of any longitudinal studies on new teacher attrition. Ingersoll adds that the new figures might be too low, and that determining the precise calculation depends on how teacher attrition is being defined. For example, does the definition include teachers who left the classroom and then returned during the first five years of their career? As a member of the advisory panel for the database that prompted the NCES study, Ingersoll is examining the raw data from that study and thinks that a more accurate figure could be higher than 20 percent.

Either way, as Ingersoll points out, the new figures are lower, which will prompt further investigation into why more new teachers are staying in the classroom.