Expert Commentary

Long-term impacts of teachers: Teacher value-added and student outcomes in adulthood

2011 study from Harvard and Columbia exploring the long-term impact on students of teachers with differing “value-added” ratings.

Teacher and student (iStock)

Education matters, both for the individual and for society as a whole. Better quality kindergarten instruction has been linked to higher earnings later in life, and children who participate in preschool programs have been shown to have lower rates of felony arrest, incarceration and substance abuse. Superior instruction in elementary and middle school could have similar benefits, but its impact is more difficult to assess because of the larger number of factors in play — including the best way to measure teacher quality. One method is the “value-added” (VA) approach, which looks at an instructor’s impact on students’ scores on standardized tests — the increasingly widespread use of which remains controversial.

A 2011 study from Harvard and Columbia universities, “The Long-Term Impacts of Teachers: Teacher Value-Added and Student Outcomes in Adulthood,” uses VA scores to explore the impact of instructors — high and low quality — on students’ lives after they leave school. The researchers, Raj Chetty, John N. Friedman and Jonah E. Rockoff, analyzed 10 years of test data from more than 2.5 million students and then looked at their rate of teenage births, college attendance, and earnings. Other factors taken into account were parents’ income levels, retirement earnings, and the mother’s age at the child’s birth. Nearly 90% of the students in the initial group were matched to later-in-life tax data, allowing the researchers to follow them from their school years into adulthood.

The study’s findings include:

  • Having a better teacher for a single grade increases by 0.5 percentage points a student’s probability of attending college by age 20. The institutions attended are also of higher quality as measured by the earnings of previous graduates.
  • Students with higher-quality teachers had “significantly higher earnings growth rates in their 20s.” Having a better teacher for a single grade increased a student’s earnings at age 28 by 1%.
  • Having better teachers was associated with a lowered probability of teenage births for a student; this factor also improved the likelihood of the students living in higher-quality neighborhoods, and increased retirement savings rates. All of these changes were “highly statistically significant,” the researchers write.
  • While some of the test-score improvement due to high-quality teachers “fades out” in subsequent grades, it stabilizes at about 33% of the original impact after three years.
  • Replacing a low-performing teacher whose value-added score is in the bottom 5% with just an average teacher would nevertheless increase lifetime income by an estimated $267,000 per classroom taught.
  • Bonuses paid to retain superior teachers were not found to be particularly successful. “Although the benefits from retaining a teacher whose estimated VA is at the 95th percentile after three years is nearly $200,000 per year, most bonus payments end up going to high-VA teachers who would have stayed even without the additional payment.”

The researchers noted several limitations of the study. First, “using VA measures in high-stakes evaluations could induce responses such as teaching to the test or cheating, eroding the signal in VA measures.” Second, “one must weigh the cost of errors in personnel decisions against the mean benefits from improving teacher value-added [ratings]. We quantified mean earnings gains from selecting teachers on VA but did not quantify the costs imposed on teachers or schools from the turnover generated by such policies.”

For more information on accountability-based classroom testing, a 2011 report from the National Research Council of the National Academies, “Incentives and Test-Based Accountability in Education,” provides valuable insight. It is the result of a nearly 10-year-long effort to better understand some of the issues surrounding standardized, large-scale testing.

Tags: children, youth, schools, teachers

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