New study confirms great teachers change lives

As the debate over teacher accountability continues to simmer, a new study has delivered important findings sure to bring discussions to a proverbial boiling point. In essence the authors found that good teachers really, really matter, and can have long-term effects on the lives and successes of their students.

According to the New York Times,the study spent 20 years tracking 2.5 million students (grades 3 through 8) in a large urban school district. Authors Raj Chetty and John N. Friedman of Harvard and Jonah E. Rockoff of Columbia, all economists, had two basic questions to guide their research:

First, do test-based measurements of teacher accountability (known to education reformers as 'value-added') accurately illustrate teachers' impact on students? And second, according the study's executive summary, "do high value-added teachers improve their students' long-term outcomes?"

The research seemed to deliver a resounding 'yes' to both questions. "It turns out that the effects of high value-added teachers in grade school continued to reverberate into adulthood," Slate reported. Students who spent even one year in grade school in the classroom of a teacher in the top 25 percent of the district were more likely to attend college (and a better college), less likely to be a teenage mother and ultimately earned a higher income as an adult.

The authors concluded that, "Teachers' impacts on students are substantial. Replacing a teacher whose true (value-added) is in the bottom 5 percent with a teacher of average quality would generate lifetime earnings gains worth more than $250,000 for the average classroom."

The researchers' method is intended to show a student's improvement on a standardized test after one year with one teacher. It also seeks to control for outside factors, thus determining what contribution that particular teacher added to that particular student's education, background notwithstanding.

Significantly, teachers who improved test scores in one school consistently outperformed their peers when moved to another. The researchers found that "the arrival of a high value-added teacher resulted in a noticeable bump up in student performance at the new school, and a significant drop in student test scores at the school she had just left," Slate reported.

These findings may dissuade some of the critics of the value-added system of evaluation, who argue that bumps in test scores could be the result of environmental or economic factors that do not reflect teacher quality.