Helen F. Ladd is a distinguished professor of public policy and economics at Duke University.

In this article, which appeared in the News-Observer in North Carolina, Ladd explains why the schools need experienced teachers, not just a steady supply of novices who serve for two or three years, then leave.

She writes:

In an effort to keep educational costs in check, America’s cash-strapped states, local school districts and charter schools are hiring less-costly novice teachers. Some of the new hires are energetic college graduates supplied for two-year stints by programs such as Teach for America.

In the late 1980s, most of the nation’s teachers had considerable experience – only 17 percent had taught for five or fewer years. By 2008, however, about 28 percent had less than five years of experience. The proportions of novices in the classroom are particularly high in schools in underprivileged areas. Some observers applaud the rapid “greening” of the teaching force because they think that experienced teachers are not needed. But this view is short-sighted. Although a constant flow of new recruits is healthy, research shows that teacher experience matters in important ways:

Experienced teachers, on average, are more effective at raising student achievement. In research I have done with colleagues in North Carolina, experienced teachers greatly boost student achievement in elementary, middle and high schools alike. This pattern holds even after we adjust for the fact that experienced teachers are more likely to work in schools with more advantaged students.

She and her colleagues recently completed a study of teacher effectiveness in North Carolina among math teachers, and they found that:

…math teachers become increasingly effective at raising student test scores through about 15 years, at which point they are about twice as effective as novices with two years of experience. The productivity gains are less dramatic for middle school English teachers but follow the same trajectory.

Experienced teachers also strengthen education in numerous ways beyond improving test scores. Our research suggests that as North Carolina middle school teachers gain experience, they become increasingly adept at producing other important results, such as reducing student absences and encouraging students to read for recreational purposes outside of the classroom. More experienced teachers often mentor young teachers and help create and maintain a strong school community.

Also, as other research has shown, constant teacher turnover is disruptive for schools and harmful to students, especially in disadvantaged schools. All too often, inexperienced teachers are initially assigned to disadvantaged schools, where the challenges of maintaining order and effectively instructing students are very high.

TFA teachers may do a good job, but by year three, more than 80% are gone, and the schools must bear the cost of recruiting, training, and mentoring another crop of novice teachers. This constant churn of staff is not good for the school community.
The challenge for public schools is to retain and support teachers as they gain experience and grow more effective. For that, they need adequate salaries and good working conditions.