The “Teacher Effectiveness” Effect

Posted on August 27, 2012

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If you’ve ever worked in education, I’d be willing to bet you’ve heard some version of the following (perhaps over and over):

“Few things will impact a child’s life more than a great teacher.”

The profound impact that teaching has on the lives of children is one of the great mantras of the profession, an education school rallying cry, and the reason so many justify a cut in pay when they choose to become teachers. Is it a platitude? Maybe. Sentimental? Absolutely.

But is it true? Do effective teachers really have such a profound effect on the lives of their students? It’s one thing for students to remember a teacher fondly, or to value what was taught, but just how intrinsically valuable is a teacher’s contribution to the quality of his or her students’ lives?

A Bill and Melinda Gates Foundation multi-year project called Measures of Effective Teaching (MET) is uncovering the answer to precisely this question—using data to measure the value of highly-effective teaching in the lives of students, and discovering exactly how to measure teacher effectiveness. Though the study is still ongoing, the results so far are enlightening.

In their preliminary findings, researchers collected data revealing that those sentimental platitudes about the influence of teachers are actually spot-on in many cases—that is, as long as the teachers are highly-skilled:

In every grade and subject, a teacher’s past track record of value-added is among the strongest predictors of their students’ achievement gains in other classes and academic years. A teacher’s value-added fluctuates from year-to-year and from class-to-class, as succeeding cohorts of students move through their classrooms. However, that volatility is not so large as to undercut the usefulness of value-added as an indicator (imperfect, but still informative) of future performance.

In other words, not only are highly effective teachers improving student outcomes in their own classrooms, the lessons they teach continue to exert an influence that causes students to elevate their performance in other classes, years later.  This trend is marked, and it is consistent—indeed a teacher’s track record of producing student achievement gains signals whether the teacher is likely to achieve similar success with another group of students.

What’s more, new data released by MET in 2012 speaks to the power of an effective teacher not just in school, but over the course of a lifetime:

We find that students assigned to high-VA [value added] teachers are more likely to attend college, attend higher quality colleges, earn more, live in higher socioeconomic status (SES) neighborhoods, and save more for retirement. They are also less likely to have children during their teenage years.

Teachers in all grades from 4 to 8 have large impacts on their students’ adult lives. On average, a 1-standard-deviation improvement in teacher value- added (equivalent to having a teacher in the 84th percentile rather than one at the median) in a single grade raises a student’s earnings at age 28 by about 1 percent. Replacing a teacher whose value-added is in the bottom 5 percent with an average teacher would increase students’ total lifetime incomes by more than $1.4 million for a typical classroom (equivalent to $250,000 in present value). In short, good teachers create substantial economic value, and VA measures are useful in identifying them [emphasis added].

My 20 years of research in education have convinced me forever that there are very few challenges in education—dropout rates, teacher retention, vouchers, class size, etc.—that can’t be solved by effective classroom teaching. I’m looking forward to following MET’s continued research on the topic.

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