One of the most popular pieces of conventional wisdom in the national debate over education is that teachers lose the capacity to further improve student achievement after only a few years in the classroom - their effectiveness plateaus early in their careers. This perception has framed debates on everything from teacher quality, professional pay, due process, and teacher retention and recruitment.

But is it supported by research? The Learning Policy Institute recently dove into existing data, surveys and reports to shed some light on the relationship between teaching experience and student outcomes.

The verdict: experience matters - even in the second decade of teaching and beyond.

"The common refrain that teaching experience does not matter after the first few years in the classroom is no longer supported by the preponderance of the research," Tara Kini and Anne Podolsky write in Does Teaching Experience Increase Teacher Effectiveness? "We find that teaching experience is, on average, positively associated with student achievement gains throughout a teacher’s career."

Based on their analysis of 30 studies published over the past 15 years, Kini and Podolsky find that:

Gains in teacher effectiveness are most striking during the first five years in the classroom, but continue to increase during the second, and often third, decade of a career.

As teachers gain experience, students' academic gains are not the only benefit. School attendance also improves.

For teachers to be effective at any point in their career, they must be a part of a supportive and collegial school environment. Stability in teaching assignments is also key. Teachers are most effective in the same grade level, subject, or district.

More experienced teachers support greater student learning for their colleagues and the school as a whole, as well as for their own students. Novice teachers, in particular, benefit most from having more experienced colleagues.

Previous research often used a “snapshot” approach to compare groups of teachers with different experience levels during a single school year, reflected in the graph on the left. More recent research has been more precise because it allows researchers to compare an individual teacher to him/herself over the course of a career (graph on the right). (Click to Enlarge)

Why take this issue on now? Aside from the fact that recent research uses more precise and accurate methods (see figure above), Kini and Podolsky say that the issue is especially relevant today. The teaching force in 2016 as a whole is "greener" than in the past and, with an influx of new teachers about to enter the profession, about to become more so. Do we focus our professional development and training resources on novice teachers or continue to invest in more experienced teachers? How do we build teaching as a respected, long-term profession? Equity continues to be a major concern. Low-income students are more likely to be taught by less-experienced teachers and attend schools with high rates of teacher turnover.

Given the stakes for the profession, the authors urge policymakers to invest in strategies that will create and sustain an experienced, skilled teaching workforce. Increasing teacher retention and reducing turnover is therefore critical. Kini and Podolsky provide three specific recommendations. First, increase stability in teaching assignments. While many teachers welcome new challenges and opportunities, school leaders should understand that educators with repeated experience at the same grade level or subject area generally improve more rapidly than those who have shifted during their career. Secondly, administrators should also make every effort to create a collaborative and collegial environment.

Lastly, the authors recommend that we strengthen policies to break up the concentration of novice teachers in high-poverty schools. They highlight the provision in the Every Student Succeds Act that specifically mandates states to monitor teacher equity gaps.

These and other policy initiatives are critical because the research does not in any way suggest that the mere "passage of time will make all teachers better or incompetent teachers effective," write Kini and Podolsky.

But the bottom line is, "a more experienced teaching workforce offers numerous benefits to students and schools, including greater individual and collective effectiveness in improving student outcomes as well as greater stability and coherence in instruction and relationship-building—the core work of schools."

Read Does Teaching Experience Increase Teacher Effectiveness? by the Learning Policy Institute.