Teacher evaluation is good personnel practice and a source of much needed feedback for every teacher, but it is often bundled with accountability policies. Given its taint as an accountability measure, it has become as politically divisive as mask wearing. On teacher evaluations, there are two distinct camps: those who claim that it is unreliable, punitive, and makes the teaching profession less attractive, and those who claim that it strengthens the teacher workforce.

The claims on both sides generally reference evaluation's impact on the current teacher workforce, but less is known about how evaluation's bad rap—getting "tougher'' on teachers—might affect the quantity or quality of new teachers available to schools.

A recently published study by Matthew Kraft (Brown University), Eric Brunner (University of Connecticut), Shaun Dougherty (Vanderbilt University), and David Schwegman (American University) sheds some light. They zero in on states adopting stronger evaluation systems and other educational reforms, while controlling for other factors such as the downturn in the economy.

Just as schools reported a higher rate of teacher attrition after implementing new teacher evaluation systems (much of which was good for teacher quality), this study finds a reduction in the supply of newly licensed teachers, attributing a 16% drop in the number of available new teachers to measures used to introduce more accountability into the profession. Evaluation reforms, they assert, were linked to a 2.6 percentage point increase in the probability that schools had at least one unfilled teaching vacancy, especially in their hard-to-staff schools.

However, Kraft et. al. note that the reduction was driven by fewer teachers coming out of less competitive institutions, a decline which led to an increase in the average quality of the new teacher pool.

Why would evaluation reform decrease the new teacher supply since these are not teachers who were yet subject to evaluation? The researchers assert that teacher evaluation reforms affect a prospective teacher's perceptions of job security, job satisfaction, and control over their teaching, which in the absence of other forms of compensation, deters prospective teachers from entering the workforce. However, individuals who are more confident in their abilities are less likely to feel 'threatened' by the new rules.

Overall, this study's findings reinforce some of the arguments in favor of accountability reforms: teacher evaluation decreases a teacher's sense of job security and in that way leads lower performing teachers to choose to filter out, be they already employed or teaching prospects. Yes, it also means that especially high-needs schools may have a harder time filling all of their vacancies, even though they tend to attract less effective teachers. The solution to this problem is not to do away with evaluation but to pay effective teachers more money to work in these schools, something we've noted more than a few times.