September 23, 2012
Rating Teachers
Rating Teachers—Posner
I know from my own educational experience that teachers differ in quality and that a good teacher improves the life prospects of his or her students, and that, as Becker says, usually it's easy to distinguish good from bad teachers ex ante, that is, before the actual impact of the teachers on their students' lives can be assessed. Everyone knows all this; the question is what to do with this knowledge in order to improve life prospects.
At the risk of sounding retrograde and unimaginative, I suggest that the only worthwhile reforms of teacher compensation are raising teacher wages uniformly, providing recognition and modest bonuses for outstanding teachers, and increasing hiring standards. The first two suggested reforms are essential because without them the third will have little or no effect on teacher quality. Per-pupil costs in American schools are high by international standards, it is true, seemingly without much to show for the high costs; but teacher salaries have to be raised in order to attract more good teachers because American women today have so much better alternative job opportunities than they used to have.
I don't think varying salaries on the basis of measures of teacher quality are a feasible reform. My reasons for this pessimistic judgment are several. First, teaching below the college level tends not to be attractive to competitive people. I happen to have a job, as a federal court of appeals judge, in which everyone is securely tenured and paid the same salary, even though the judges vary in ability, experience, and effort. There are many jobs of that sort, they have their pluses and their minuses, and it would be a mistake to think that all such jobs would be performed better if they were restructured along the Darwinian lines that prevail in business. It's a mistake to think that everyone is a natural risk taker. Tenure, a wage that varies with seniority rather than measured output, and long summer vacations create a compensation package that is attractive to a certain kind of person.
Second, while in a sample of millions, as in the study by Chetty et al. that Becker cites, it may well be inferrable, as the study finds, that teachers vary in the value they add to their students, within an individual school such an inference will be very difficult to draw. The average IQ and home environment of students in different classes may differ significantly, random factors may affect their future success, and there can be spillover effects from other classes. Suppose for example that a mediocre teacher teaches English, and a superb teacher teaches the same students history. Both teachers require essays. The superb teacher improves the students' writing skills, and that in turn improves their performance in their English class, making the English teacher look better than he or she really is.
Third, and related, varying teachers' salaries by some output measure will induce all sorts of wasteful strategizing—office politics—what organization economists call "influence activities," an aspect of agency costs—by teachers hoping to get a good quality rating. They will angle to get the best students assigned to their classes, even when salary is tied to "value added," as discussed by Becker, because smarter students are likely to improve more.
Fourth, although in principle the cost of higher salaries for the better teachers could be offset by reducing the salaries of the worse teachers, that is surely infeasible; so the Darwinian approach would cost more than the existing system, and maybe as much more as raising teacher salaries by a uniform percentage.
Finally, I am not clear what we should think the problem of American education (below the college level) is. Most children of middle-class (say upper quartile of households, income starting at $80,000) Americans are white or Asian and attend good public or private schools, usually predominantly white. The average white IQ is of course 100 and the Asian (like the Jewish) almost one standard deviation higher, that is, 115. The average black IQ is 85, a full standard deviation below the white average, and the average Hispanic IQ has been estimated recently at 89. Black children in particular often come from disordered households, which has a negative effect on ability to learn and perhaps indeed on IQ (which is only partly hereditary) as well. Increasingly, black and Hispanic students find themselves in schools with few white or Asian students. The challenge to American education is to provide a useful education to the large number of Americans who are unlikely to benefit from a college education or from high school courses aimed at preparing students for college. The need is for a different curriculum and for a greater investment in these children's preschool environment. We should recognize that we have different populations with different schooling needs and that curricula and teaching methods should be revised accordingly. This recognition and response should precede tinkering with compensations systems.
Good and Bad Teachers: How to Tell the Difference-Becker
Although the recent Chicago teachers' strike of seven school days was their first strike in 25 years, the main disagreement with the city was not over the traditional bread and butter issue of pay and benefits. Rather it was centered on the criteria to be used in evaluating teachers to distinguish good teachers from bad ones. It might seem surprising that teacher evaluations were so contentious since the union had already forced Mayor Rahm Emanuel to take merit pay for good teachers off the negotiating table. However, being deemed a good teacher still has advantages, including that better-rated unemployed teachers receive higher priority when teaching positions become available.Moreover, the union is aware that merit pay will become more of an issue in the future.
Teacher unions have long argued that the main criteria to be used in determining whether teachers are effective or not should be variables like teaching experience and teaching credentials rather than subjective evaluations of principals and other administrators. The unions claim that these evaluations were likely to be biased because allegedly they would be greatly affected by whether administrators liked or disliked particular teachers instead of by their actual classroom performance.
Unions and their supporters have also argued that teacher evaluations by administrators or parents are not worth a lot because it is difficult to get agreement on who are the good and bad teachers. I would challenge that claim: most of the time students as well as teachers agree on who are the good and bad teachers. Even my grandchildren in the lower grades of elementary school are confident that they and other students know which teachers to avoid, and which to try to get. Nevertheless, to provide more objective measures, teacher evaluations have been shifting toward using performance on standardized tests that measure knowledge of math, science and English language-related subjects. Teachers whose students perform well on these tests are deemed good teachers, whereas those with poorly performing students are considered weak teachers.
Teacher unions all over the country have fought against using performance-based measures to evaluate teachers, but the unions are gradually losing this battle. More than half of all U.S. states have adopted policies that require teachers to be rated in part based on student performance, such as standardized test scores. Even in their "victory" in the Chicago strike, the teachers union could not eliminate the use of student performance measures in evaluating teachers, but succeeded only in getting its weight in teacher evaluations down to 25% in the first two years of the contract, 30% in the third year, and 40% in year 4-the city wanted a weight of 40% starting in teh first year of the contract.
Of course, actual test scores are not appropriate measures of teacher contribution since some teachers get students who are better prepared when they enter their classes. For this reason the criterion used in evaluating teachers by many school systems and also by academic articles on school reform is the value added (VA) by teachers to student performance; namely, the improvements in students' test scores as a result of taking classes of different teachers. The New York Times and the Los Angeles Times have in recent years released VA results for some the teachers in the New York and Los Angeles school districts, despite the loud protests of teachers unions in these cities.
Even value added may not fully measure the relevant effects of teachers on student performance since, for example, a given improvement in test scores may be more (or less) important for students with low test scores than for those who had high scores. More importantly, the fundamental way to judge teachers is not how their students do on tests, but how different teachers affect the likelihood that their students finish high school and go to college, how teachers affect the earnings of their students after they enter the labor force, and whether their students get involved in gangs and crimes.
A small number of recent academic studies have tried to see how well VA measures predict how students do when they become adults. A summary of a good study along these lines by Raj Chetty, John Friedman, and Jonah Rockoff was published this summer in the journal Education Next under the title "Great Teaching". They had access to data for a large urban school district that spanned the 20 years from 1988-89 through 2008-09. The data contained information on test scores for about 2.5 million children in grades 3 through 8, and also the schooling, and when available, earnings of the children after they finished these grades.
They find large effects on subsequent adult earnings when these young students had teachers who produced good improvements in test scores compared to the adult earnings of students who had teachers who produced little improvement in test scores. If teachers were paid in relation to their effects on the subsequent adult earnings of their students, these results imply that teachers with good VA ratings should be paid considerably more than teachers with bad ratings. Adopting such a payment system for teachers would produce an improvement in the quality of teaching because good teachers would be more willing to go into teaching at elementary and high school grades. Such a change may well induce an increase in overall spending on teachers' salaries and benefits because taxpayers would be willing to support education more generously if they felt students were getting good and useful teaching.
Of course, further studies of the effects of teachers on value added and on variables like adult earnings may find much smaller effects than those found by Chetty, et al. Yet their finding that good teachers make a big difference to student performance is not the least bit surprising. This makes it all the more unfortunate that for decades teachers unions have fought against merit pay for good teachers, no matter how "good" teaching were to be measured. Since parents are losing patience with bad teachers, I expect the issue of merit pay to be one of the coming battlegrounds between teachers unions, and school boards and parents that want to better prepare students for the rigors of the modern marketplace.