Thursday, January 12, 2012

Do Teachers Matter?

According to this new paper at the NBER, yes they do (abstract):

The Long-Term Impacts of Teachers: Teacher Value-Added and Student Outcomes in Adulthood
Raj Chetty, John N. Friedman, Jonah E. Rockoff

Are teachers’ impacts on students’ test scores (“value-added”) a good measure of their quality? This question has sparked debate largely because of disagreement about (1) whether value-added (VA) provides unbiased estimates of teachers’ impacts on student achievement and (2) whether high-VA teachers improve students’ long-term outcomes. We address these two issues by analyzing school district data from grades 3-8 for 2.5 million children linked to tax records on parent characteristics and adult outcomes. We find no evidence of bias in VA estimates using previously unobserved parent characteristics and a quasi-experimental research design based on changes in teaching staff. Students assigned to high-VA teachers are more likely to attend college, attend higher- ranked colleges, earn higher salaries, live in higher SES neighborhoods, and save more for retirement. They are also less likely to have children as teenagers. Teachers have large impacts in all grades from 4 to 8. On average, a one standard deviation improvment in teacher VA in a single grade raises earnings by about 1% at age 28. Replacing a teacher whose VA is in the bottom 5% with an average teacher would increase students’ lifetime income by more than $250,000 for the average classroom in our sample. We conclude that good teachers create substantial economic value and that test score impacts are helpful in identifying such teachers.

There’s a difference of opinion regarding whether tests actually measure learning, and more importantly how they impact children as they enter adulthood. Given that problem, are teachers whose teaching improves tests scores really good teachers (and should be compensated as such)? In the sense of improving lives in adulthood? This paper attempts to answer both questions at once, and generally finds that, yes, both tests and teachers who improve test scores among their charges do make a difference later in life.

You might think this is an idiotic question for researchers to look at – some of us remember devoted and dedicated teachers who’ve inspired us to do better, and there’s always those forgettable ones who seemed to just punch in and punch out.

But when we’re talking about making changes at a policy level when many lives and future lives are at stake, objectivity is terribly important.

Now as to the question of whether particular tests and certificates are good indicators of learning, that’s another matter, as the paper is focused on US data not Malaysian. Maybe somebody in Malaysian academia might want to take this up – do the number of A’s at SPM really equate to better life outcomes, after taking into account parental background, teacher/school quality and aptitude? And would SPM achievement signal anything about the ability adapt and excel in university and in the workplace?

Technical Notes

Chetty, Raj and John N. Friedman & Jonah E. Rockoff, "The Long-Term Impacts of Teachers: Teacher Value-Added and Student Outcomes in Adulthood", NBER Working Paper No. 17699, December 2011

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