I like to think that as students our ability in distinguishing good from bad professors became refined over the years (I bet you are thinking on a few that fit these two categories!). However, our judgments are purely based on our preferences and they are worth what they are worth. It is not unusual that within your group of friends some like one teacher while others don’t. Some attach an approval stamp because of the teacher’s technical knowledge, others because of the teacher availability in answering questions and dedicating time to students outside the classroom, and others because they get a high grade in the respective course.
In this post, I want to address two questions intrinsically related: The first concerns teacher effect on students’ outcomes, and the second relates to teacher characteristics and how to consider them in measuring teacher quality.
Starting with the first question, and coming across some literature, I was surprised on how Hanushek (1981, 1986, 1996, 1997) concluded, in a series of studies, that educational inputs and students achievements are not systematically correlated, and, in many cases, what he considered to be measures of teacher quality, such as teacher education, teacher test scores and teacher experience, are not statistically significant for students’ outcomes. However, his claim has been highly challenged since then.
In 2003, and moving into the second question I proposed for this post, Jennifer Rice, from the Univeristy of Maryland, wrote that “a particular teacher attribute may be an important predictor of teacher effectiveness in some contexts but may not matter at all or may even have a negative effect in other contexts”. As so, she included in her research contextual variables such as the level of education that is being teached as well as the subject area. She found that teacher degrees are particularly important for student achievement at the secondary level, especially in the areas of mathematics and science, and also that pedagogical coursework (learn how to teach) is very important at all levels, namely in combination with content knowledge (knowledge of the subject). As a result, highly qualified teachers may not necessarily be high quality teachers.
More recently, Raj Chetty, John N. Friedman and Jonah E. Rockoff (2011) studied the teachers’ impact on students’ outcomes via the teachers’ “value-added” (VA) approach, defined as the average test-score gain for his or her students. Using a natural experiment arising from random teacher turnover, the authors argue that if test scores rise immediately after the teacher arrival to school and fall when he/she leaves, then he/she must be considered a high VA teacher. Following this identification method, the most striking point of their work regards the long-term effects of teacher quality, namely on students’ future earnings. According to them “replacing a teacher whose true VA is in the bottom 5% with one of average quality would generate cumulative earnings gains of $52,000 per student”.
In the end of the day, teachers seem to matter, not only in short but also in long terms. Shouldn’t countries be committed in designing and implementing effective teachers’ evaluation schemes? Clearly yes. The problem is no one really knows what makes a good teacher…
Rice, J. (2003) Teacher Quality: Understanding the Effectiveness of Teacher Attributes, Economic Policy Institute
Chetty, R., Friedman, J., Rockoff, J. (2011) “The Long-term Impacts of Teachers: Teacher Value-added and Student Outcomes in Adulthood”, Executive Summary of National Bureau of Economic Research Working Paper No. 17699