How important is a good teacher? That question has been the subject of intense debate over the past several years. Although most people agree that a good primary school teacher is incredibly valuable, how to define a good teacher is quite difficult, and defining a poor teacher is even more challenging. One controversial way to assess the quality of a teacher is through use of value-added ratings. Most simply, value-added ratings compare the test scores of students for a teacher in one year to test scores of previous years and are also compared to students of other teachers. Previous research has shown that the positive effect of a single teacher on the subsequent scores of students fades within a few years.
As reported in The New York Times (Education: January 6, 2012), a large study that looked at 2.5 million students for more than 20 years, concluded that good teachers have a lasting impact not just on student test scores but on many other measures including adult income. The researchers used value-added ratings to characterize elementary and primary school teachers as good, average, or poor. Students of teachers characterized as good had lower teenage-pregnancy rates, were more likely to attend college, and had greater adult earnings. The impact of a single teacher on a single student is quite small. For example, having a single good teacher rather than all average teachers between fourth and eighth grade may result in a net increase in adult lifetime income of only $4,600.
However, if the results of an entire class are aggregated over time, the total effect becomes quite large. Importantly, the difference between poor and average was just as large and strong as the difference between good and average. The implications are that given the challenge of finding, hiring, and training good teachers, weeding out poor teachers may be more valuable. Of course, the use of value-added ratings is quite controversial. Some school officials argue that teachers may be unfairly singled out for dismissal or that if high value-added ratings become critical to job security, teachers may begin teaching to the test. Regardless, the data shows that having either good or poor primary or elementary school teachers has a lasting impact on student lives. This is just one way to identify those teachers.
Noted by WVR, MD
*This filler excerpt can be found in the April 2012 Pediatrics print journal p. 708, or via online here.
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