Principal investigator: Viviane Pires Ribeiro
Article title: MEASURING THE IMPACTS OF TEACHERS II: TEACHER VALUE-ADDED AND STUDENT OUTCOMES IN ADULTHOOD
Article authors: Raj Chetty, John N. Friedman and Jonah E. Rockoff
Location of the intervention: United States
Sample size: Approximately 2,5 million children
Main theme: Education
Type of Intervention: The impact of teachers on students' long-term outcomes.
Main Variable of Interest: Added Value of the Teacher
Evaluation method: Test Score
Evaluation Context
One prominent, yet controversial, method is evaluating teacher effectiveness based on their impact on student test scores, commonly referred to as the Added Value (AV) approach. Major school districts have already adopted the use of AV to evaluate teachers, such as districts in Washington, D.C., and Los Angeles. Some authors argue that selecting teachers based on their added values can lead to substantial gains in student performance, while others, more critically, claim that these are not good measures for assessing teacher quality.
Intervention Details
Chetty et al. (2014) studied the long-term impacts of teachers using school and tax records for over one million children. Information on students—including enrollment history, test scores, and teacher assignments—was obtained from the administrative records of a large urban school district. This data spans the school years 1988–1989 to 2008–2009 and covers approximately 2,5 million children in grades 3–8. Conversely, information on students' outcomes in adulthood was obtained from United States federal income tax returns from 1996 to 2011.
School district records were linked to tax data using an algorithm based on standard identifiers (date of birth, state of birth, gender, and names), after which individual identifiers were removed to protect confidentiality. In total, the authors combined approximately 90% of the observations from the school district data with the tax data, thus allowing them to track nearly one million people from elementary school to early adulthood in order to measure outcomes such as salary, college attendance, and... fee birth rate teenagers.
Methodology Details
Two research designs were used to estimate the long-term impacts of teacher quality: cross-sectional classroom comparisons and a quasi-experimental design based on teacher turnover. The first design compares student outcomes for teachers with different VA (Value Added), controlled for a set of student characteristics such as scores on previous tests and demographics. The authors implemented this approach by regressing long-term outcomes on VA estimates from test scores. The underlying identification assumption of this design is the selection of observables: unobserved determinants of outcomes in adulthood (such as student ability) should not be related to teacher VA, depending on observable characteristics. Conversely, the second design relaxes this selection of observables assumption by exploring teacher turnover as a quasi-experimental source of variation in teacher quality.
Results
In the first research project, the results found by Chetty et al. (2014) show that a one standard deviation improvement in the added value of the teacher in a single grade increases the likelihood of students attending college at age 20 by 0,82 percentage points, relative to a sample average of 37%. Improvements in teacher quality also increase the quality of the colleges students attend, as measured by the average earnings of previous graduates.
Students who study with teachers with higher VA (Value Added) experience steeper earnings trajectories in their 20s. That is, at age 28, a one standard deviation increase in the teacher's VA in a single grade increases students' annual earnings by 1,3%. If the impact on earnings remains constant at 1,3%, students will receive an average of $39.000 in accumulated lifetime income. Discounting at a rate of 5% generates a present value gain of $7.000 at age 12, the average age of the students.
Improvements in the quality of teaching by teachers significantly reduce the likelihood of students having a child during adolescence, increase the quality of the neighborhood in which the student lives in adulthood (measured by the percentage of graduates from that zip code), and increase participation rates in retirement plans.
In the second project, the results show that a one standard deviation improvement in the teacher's VA increases the probability of students attending college at age 20 by 0,86 percentage points, a value almost identical to the estimate obtained in the first project. Improvements in the average VA of teachers also increase the quality of the colleges that students attend.
Lessons in Public Policy
Do high-value-added teachers improve long-term student outcomes? The results found by Chetty et al. (2014) show that test score value-added measures are a good indicator. proxy Informative on the long-term impacts of teachers. In this sense, students assigned to high-value-added teachers are more likely to attend college, receive higher salaries, and are less likely to have children as teenagers. Replacing a teacher whose added value is less than 5% with a teacher of average added value would increase the present value of students' lifetime income by approximately US$250.000 per classroom.
The authors state that two issues must be resolved before determining the use of value-added in educational policymaking. First, the use of this measure to evaluate teachers may induce responses such as test-taking or cheating. Thus, it is possible to estimate the magnitude of such effects through the analysis developed by the authors in a district that evaluates teachers based on their value-added. Second, the long-term impacts of evaluating teachers based on value-added should be compared to other metrics, such as core assessments or classroom observations.
However, regardless of whether added value is used as a policy tool or not, the results show that parents should value having their children in the classroom of a high-value-added teacher, and the improvement in the quality of teaching will likely bring economic and social benefits.
References
CHETTY, Raj; FRIEDMAN, John N.; ROCKOFF, Jonah E. Measuring the impacts of teachers I: Evaluating bias in teacher value-added estimates. American Economic Review, vol. 104, no. 9, p. 2593-2632, 2014.
