How To Measure Teacher Quality?

A blog about business and economics.
Sept. 13 2012 11:43 AM

Value-Added Models of Teacher Quality

As I wrote earlier, the Chicago teachers' strike is not primarily about salary, but salary is relevant. Chicago teachers are well-compensated, which is appropriate, but the question facing the city of Chicago is whether it's getting high quality in exchange for its money.

There are a number of dimensions to the dispute around this, but the key one is that there's a trend in policy circles to push for more reliance on value-added models of teacher performance. The way VAM works, more or less, is that you use standardized tests to determine whether students are learning. But of course that would be much too crude. Parents' income and educational status and so forth is also going to affect how much kids learn. My dad dropped out of high school and could never help me with math homework the way my mom could. If neither of my parents had finished 10th grade, I would have done worse in math through no fault of my teachers. So the VAM models at issue apply various demographic controls.


Teachers and their unions are not big fans of these models. This epic John Ewing post at Valerie Strauss' Answer Sheet blog rounds up skeptical research. One key point the skeptics raise is that there's a lot of year-to-year instability in how teachers score on these models.

On the other hand, this paper from Raj Chetty, John N. Friedman, and Jonah E. Rockoff (PDF) is a typical example of the kind of research that's persuaded VAM fans that this is a good way to proceed:

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 improvement 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 the present value of 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.

I am basically on Team Chetty with regard to this. Others will disagree. But contrary to the impression you'll get reading blogs, it really isn't a question whose answer can be deduced from ideological first principles. My general view is that the wise politician will simply take the fact that teachers don't like being evaluated this way at face value and will offer them more money in exchange for accepting it (that's what we've done in Washington). The Rahm Emanuel approach of pushing an unpopular evaluation model concurrently with a longer school year and other teacher-unfriendly measures produces a backlash, and he seems to be losing in the court of public opinion.*

Politicians sometimes forget that "politician" is one of the least-respected professions in America, so any time there's a standoff between politicians and some better-regarded group of people—cops, firefighters, teachers, military officers, doctors—the tendency is for the politicians to lose.

Correction, Sept. 13, 2012: This post originally misspelled Rahm Emanuel's last name.



Blacks Don’t Have a Corporal Punishment Problem

Americans do. But when blacks exhibit the same behaviors as others, it becomes part of a greater black pathology. 

I Bought the Huge iPhone. I’m Already Thinking of Returning It.

Scotland Is Just the Beginning. Expect More Political Earthquakes in Europe.

Lifetime Didn’t Think the Steubenville Rape Case Was Dramatic Enough

So they added a little self-immolation.

Two Damn Good, Very Different Movies About Soldiers Returning From War

Medical Examiner

The Most Terrifying Thing About Ebola 

The disease threatens humanity by preying on humanity.

Students Aren’t Going to College Football Games as Much Anymore, and Schools Are Getting Worried

The Good Wife Is Cynical, Thrilling, and Grown-Up. It’s Also TV’s Best Drama.

  News & Politics
Sept. 19 2014 9:15 PM Chris Christie, Better Than Ever
Sept. 19 2014 6:35 PM Pabst Blue Ribbon is Being Sold to the Russians, Was So Over Anyway
Inside Higher Ed
Sept. 19 2014 1:34 PM Empty Seats, Fewer Donors? College football isn’t attracting the audience it used to.
  Double X
The XX Factor
Sept. 19 2014 4:58 PM Steubenville Gets the Lifetime Treatment (And a Cheerleader Erupts Into Flames)
  Slate Plus
Slate Picks
Sept. 19 2014 12:00 PM What Happened at Slate This Week? The Slatest editor tells us to read well-informed skepticism, media criticism, and more.
Brow Beat
Sept. 19 2014 4:48 PM You Should Be Listening to Sbtrkt
Future Tense
Sept. 19 2014 6:31 PM The One Big Problem With the Enormous New iPhone
  Health & Science
Medical Examiner
Sept. 19 2014 5:09 PM Did America Get Fat by Drinking Diet Soda?   A high-profile study points the finger at artificial sweeteners.
Sports Nut
Sept. 18 2014 11:42 AM Grandmaster Clash One of the most amazing feats in chess history just happened, and no one noticed.