Do we know what a teacher’s impact really is?

The factors that impact student achievement are as multi-faceted as human-beings are themselves.   An abbreviated list of these components includes: home background, community framework, individual motivation and aptitude, peer morale, prior schooling, student attendance, school culture and leadership, and of course effectiveness of the student’s teacher.  For the sake of simplicity, a number of studies have grouped together all school aspects under the category of “teacher effectiveness” and grouped all individual student and outside factors into a category called “student background,” while other studies have created a third category that makes teacher effectiveness distinct from all other school factors.  For the sake of accuracy, one could argue that these categories are not just simplifications but oversimplifications. 

Nonetheless, American education policymakers are concerned with two issues in particular: The large achievement gap between white students and minority students and the reality that American students score in the middle to bottom when compared to other industrialized countries in international tests.  Education reformers want to progress frontward on these issues but need to first pinpoint where changes in the system need to be made.  In order to do this, one question keeps coming up: Which factors impact students the most when it comes to academic success and how much weight can be placed on each of the “simplified” categories?

To fully understand the “teacher effectiveness” category that is often referred to as such by the media and by articles that cover this area, it is crucial to understand that this grouping covers more than just the characteristics and behaviors of the teachers.  This category also includes available instructional materials and resources, district and state policies that directly affect classroom occurrences, and the curriculum, which is almost always out of the teacher’s control.  “All other school factors,” which is sometimes a category by itself, includes such issues as the climate and policies of a school, the quality of a school’s staff as a whole, parent involvement, and peer culture.

“Student background” comprises all other issues, however some issues like chronic tardiness and attendance history rarely make the headlines.  When talking about “student background,” family values and socio-economics usually come to mind.  This category also encompasses emotional and physical medical history, as well as the quality of schooling the student has had in prior years. 

So is there an overall consensus on the impact certain variables have on student achievement?  According to a study from 2000, “school-level and teacher-level factors account for approximately 20 percent of the variance in student achievement.  Student characteristics–home environment, learned intelligence/background knowledge, and motivation account for 80 percent of the variance…”.  Kirsten Miller points out in her brief, School, Teacher, and Leadership Impacts on Student Achievement, that when the teacher and the school are separated, the teacher has a 13 percent variance, whereas the school has a seven percent variance.  Most research conducted on this topic uses the Marzano study from 2000, however, inconsistencies with these numbers started to become apparent upon reading Dan Goldhaber’s article, The Mystery of Good Teaching.  Goldhaber notes that “student background” actually only accounts for 60 percent of student achievement and goes on to point out that his findings reflect those of Economists Eric Hanushek, John Kain, and Steven Rivkin.  He does note that it is rare for these variables to actually be measured in isolation, though. 

Although certain economists and journalists seem to be at odds over exactly what percentage “student background” accounts for, they do agree that this category has the biggest impact on student achievement.  With that said, the 20 to 40 percent (depending on the study) attributed to the combined school and teacher factors are still enough to make a significant difference in a student’s academic school year  A look at The Center’s Teacher Quality and Student Achievement report,  shows that students who had three effective teachers would score over 50 percentile points higher than if they had three ineffective teachers. That is enough difference for a student to be recommended for honors courses or designated for remedial help simply due to the effectiveness of the teachers they were assigned over three years (this fun video explains further).  There does not seem to be a consensus but that does not mean policymakers cannot be focused in their approach to arm American schools with even more talented teachers, in-depth curriculum, and encouraging school environments. -Mandy Newport

For more information about measuring teacher effectiveness check out How good are your teachers? and Building a better evaluation system.

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