Good Teachers Can Change Kids' Lives

Guest blog by Eric Lerum, VP for National Policy, StudentsFirst

01/20/12

A groundbreaking new study (here) for the National Bureau of Economic Research by researchers from Harvard and Columbia provides important new information for guiding how we think about building and implementing meaningful teacher evaluation models. First, effective teachers are highly correlated with positive impacts both inside and outside the classroom.  Second, value-added models based on growth in student test scores are able to differentiate and identify effective teachers clearly and with significant accuracy.

These findings are particularly notable because they address key concerns about the use of value-added measures based on student achievement growth in teacher evaluations and personnel decisions. The study indicates that what we can estimate in terms of a teacher’s impact on student achievement is also highly predictive of the impact the teacher will have on a student’s life trajectory.

The Study

The report analyzed school district data for grades 3 through 8 for 2.5 million children over 20 years, and linked that data to tax records to identify parent characteristics and adult outcomes. Because of the unprecedented scope in time-series and sample size, the study is able to address one frequent criticism of value-added testing: that it often produces great variance in scores as a teacher moves from class to class. But in looking at individual teachers’ value-added scores, the researchers found that some consistently outperformed their peers.

The Findings: Better Student Outcomes With Better Teachers

The study found that students who had teachers that were identified as effective (by their value-added scores, based on student test performance and growth) were more likely to attend college, attend higher- ranked colleges, earn higher salaries, and live in better neighborhoods, and had lower rates of teen pregnancy. These teachers were clearly linked to better life outcomes and strong success in the student’s future educational and career endeavors.

Moreover, even marginal improvements to the quality of a student’s teacher were directly linked to a measureable increase in earnings later in life. For instance, replacing a teacher whose effectiveness was rated in the bottom 5% with an average teacher would increase lifetime earnings for the average classroom by more than $250,000. The authors conclude: “good teachers create substantial economic value and that test score impacts are helpful in identifying good teachers.”

Students Learn More From Good Teachers

The authors set out to test the question of whether teachers whose students score well on tests genuinely improve student outcomes, or are simply better at “teaching to the test.” In addition to finding that effective teachers produced a variety of positive life outcomes and drove student success, they also found that the gains from effective teachers stayed with students well into the student’s future. While gains from the initial year do fade out over time, the report indicates that they stabilize at about 1/3rd of the original impact after three years, showing that a solid amount of the achievement gains persist.  In sum, good teachers do not appear to be simply teaching to the test and in fact genuinely improve long-term student outcomes.

Value-Added Models Identify Teachers Who Are Great, and Those Who Aren’t 

The study finds that a teacher’s value-added scores are clearly predictive of the success they will have in teaching students, and therefore the success the students themselves will achieve, in their scores on assessments and in other indicators outside of and after they complete school. As the study’s authors write, “the findings in this paper and prior work are sufficient to conclude that standard estimates of teacher [value-added] can provide accurate forecasts of teacher’s average impacts on student’s test scores.” They also note that “good teachers create substantial economic value and that test score impacts are helpful in identifying such teachers.”

Thanks to the massive scope of the study, the potential for variance due to differences among the students in different classrooms that some critics point to appears to be minimal. As the New York Times put it, "the researchers found that some [teachers] consistently outperformed their peers," regardless of the classroom they were leading.

Conclusion

This high quality, exhaustively researched study confirms and lends even greater credibility to what previous research has shown us: quality teaching is the key factor in student outcomes; students learn more from high performing teachers; and value-added models effectively identify high performing teachers and those who need additional development. In short, it confirms what anyone who has ever had a great teacher knows already – great teachers matter. They have a huge impact, and that impact lasts well beyond the classroom.

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