There is widespread agreement that one of the most reliable ways to improve the quality of K-12 instruction in the United States is to increase average teacher quality. But this raises two crucial and interrelated questions: (1) how should we measure teacher quality? And once we agree on (1), (2) how should we actually go about increasing average teacher quality?
Conventional measures of teacher quality include years of experience and attainment of advanced degrees. These are the indicators that are entrenched in salary schedules in school districts across the country, and that have been adamantly defended by teachers unions. Yet as Duke University economist Jacob Vigdor has found, the value of additional years of experience increases rapidly in the first few years before leveling off and advanced degrees appear to have no impact on effectiveness in the classroom.
As Marcus Winters recounts in an article in the Fall 2012 issue of National Affairs, there is another approach to assessing teacher quality:
Value-added analysis predicts how well a student should perform in a given year based on a series of observable factors that are related to his academic achievement, but are beyond a teacher’s control — factors such as race, gender, and family income. The analysis then compares for each teacher the estimate of how well his students were expected to perform at the end of the school year given the characteristics they brought into the classroom with their actual test scores in the spring. The teacher’s VAM score represents his performance in standard-deviation units relative to the average teacher (the mean VAM score) in the school system; the mean score is set at zero. If a teacher’s students tend to outperform expectations on average, then the teacher’s VAM score will come back as positive; if students perform worse than expected given their characteristics, the teacher will receive a negative VAM score.
It is easy to understand why teachers might resist value-added analysis. Winters gives careful consideration to arguments against value-added analysis, and he is very open about its weaknesses. He nevertheless sees it as an important step forward.
My own strong preference would be for pluralism in this space. That is, different schools will pursue different business models, and teachers will negotiate their contracts as individuals in keeping with their needs and ambitions. But value-added analysis is designed to offer an alternative to conventional measures of teacher quality that is similarly compatible with centralized school governance and collective bargaining. This disagreement is perhaps best seen through the lens of Neerav Kingsland’s contrast between “relinquishers,” who aim to relinquish the power of centralized bureaucracies in favor of a wide array of instructional providers, and “reformers,” who aim to improve the performance of centralized systems.
One thing that is interesting about the shift from our aforementioned (1) to (2) is that teachers unions tend to emphasize higher compensation levels and smaller class sizes as the best way to improve average teacher quality. The idea, as I understand it, is that higher compensation levels will allow public schools to attract and retain better teachers, or rather to give teachers the respect they deserve, etc. Smaller class sizes, meanwhile, will improve teacher effectiveness.
There is a problem with this line of thinking. Reducing class sizes will mean increasing hiring, which will increasing the compensation budget for school districts even if compensation levels remain the same. To increase class sizes at the same time that we increase compensation levels would mean either allowing compensation to crowd out other educational expenditures or increasing educational budgets. The decidedly ambiguous evidence in favor of reduction suggests that this is not a good bet, particularly since it would be far easier to increase compensation levels if we allowed for somewhat higher student-teacher ratios.
If we instead allowed the most effective teachers to take on more students in exchange for more compensation, as under the Gold Star Teachers proposal, we could rapidly improve the quality of teaching experienced by the median student. But of course something like the Gold Star Teachers proposal in an existing school district — as opposed to a “relinquished” charter school district — would have to rest on something like value-added analysis.