It's almost accepted as fact now that teachers don't improve much after their first few years on the job. New research challenges this assumption.
Efforts to improve the quality of the teacher workforce have risen to the top of the education policy agenda during the past decade. More than ever, policymakers are drawing on research to inform their positions. One research finding that policymakers cite consistently in conversations about teaching quality is that teachers face a "performance plateau" after their first few years of teaching.
On average, the argument goes, teachers don't improve their effectiveness after their first several years in the classroom. For much of the past decade, this "performance plateau" has been characterized as a fact in the research literature (Rice, 2013), and this idea has profoundly affected education policy. For example, a 2012 fact sheet by TNTP (formerly known as The New Teacher Project) reported that "teachers gradually reach a plateau after 3–5 years on the job," and Bill Gates asserted in 2009 that "once somebody has taught for three years, their teaching quality does not change thereafter."