First Impressions: Best and Worst Teachers

I heard from several senior colleagues of mine that a good teacher is really easy to spot. The engaging manner and dedication apparently manifest even in the very first lecture of a good teacher. These opinions raise the question of whether effective teaching is an innate talent or an acquired skill. This is an important question since its answer can help guide time and resources allocation on teacher training programs. There is no doubt that experience has significant effects on a teacher. It is quite reasonable to guess, however, that the improvements in teaching over the years due to experience decrease over time. As Sarah D. Sparks of Education Week wrote in her article, "Best and Worst Teachers Can Be Flagged Early, Says Study":
New teachers become much more effective with a few years of classroom experience, but a working paper by a team of researchers suggests the most—and least—effective elementary teachers show their colors at the very start of their careers.
Sparks is referring to the following study from the National Center for Analysis of Longitudinal Data in Education Research:
The above is still a working paper. It has not been peer reviewed. The following is its abstract:
There is increasing agreement among researchers and policymakers that teachers vary widely in their ability to improve student achievement, and the difference between effective and ineffective teachers has substantial effects on standardized test outcomes as well as later life outcomes. However, there is not similar agreement about how to improve teacher effectiveness. Several research studies confirm that on average novice teachers show remarkable improvement in effectiveness over the first five years of their careers. In this paper we employ rich data from New York City to explore the variation among teachers in early career returns to experience. Our goal is to better understand the extent to which measures of teacher effectiveness during the first two years reliably predicts future performance. Our findings suggest that early career returns to experience may provide useful insights regarding future performance and offer opportunities to better understand how to improve teacher effectiveness. We present evidence not only about the predictive power of early value-added scores, but also on the limitations and imprecision of those predictions.
It should be noted that this longitudinal study has been hampered by a general lack of permanence in teachers' assignments. For a valid comparison throughout five years, teachers need to be teaching the same class. Unfortunately, only five percent of the New York City teachers continued to teach the grades (4 and 5) that were chosen by this study. This makes the study highly selective therefore raising the validity of the conclusions drawn. It is unfortunate that the teaching profession currently has a high attrition rate. Thus, the following findings should be taken with a grain of salt:
"We find that, on average, initial performance is quite predictive of future performance, far more so than measured teacher characteristics such as their own test performance (e.g. SAT) or their educational experience.On average the highest fifth of teachers remain the highest fifth of teachers; the second fifth remains the second fifth; the third fifth remains the third fifth; and so on. Predictions are particularly powerful at the extremes. Initially excellent teachers are far more likely to be excellent teachers in the future than are teachers who were not as effective in their first few years."
The above findings are quite powerful. The first few years of a teacher somehow can tell the entire story. This is highlighted in the following figure:

Figure downloaded from
The first two years do show marked improvement especially for the least effective new teachers. What is interesting is that the next three years show a plateau for all quintiles. Although the study is quite selective as it excludes teachers who have left, these results are still highly informative. First impressions do matter.