When the Obama administration and states across the country embraced tougher evaluation and tenure rules for teachers, critics offered a familiar refrain: weakening teachers’ job security could make the profession less attractive and ultimately backfire.

Now a new study is among the first to suggest that this concern has become a reality, showing that after states put in place new evaluation and tenure rules, the number of new teaching licenses issued dropped substantially — a finding that researchers said suggests fewer people were interested in the job.

“We find consistent evidence that both implementing high-stakes evaluation reforms and repealing tenure reduced teacher labor supply,” concludes the paper, which controlled for a number of factors that might have affected the pool of teachers.

The study does not attempt to show any potential benefits of such reforms — and other research paints a more encouraging picture — but the latest analysis raises a caution flag for those insisting on tighter accountability for teachers.

Jason Grissom, a professor at Vanderbilt University, examined the paper, which has not been formally peer-reviewed, at Chalkbeat’s request and praised its approach: “The study is carefully done using standard methods in the field.”

However, Grissom pointed to one reason the impacts may not be as harmful as they might seem at first glance. “We don’t know whether the teachers who chose not to become licensed may have been less effective teachers,” he said. “If so, we can’t interpret the negative effects on new teacher supply as necessarily negative for the system overall.“

Matt Kraft, a Brown University professor and one of the study’s authors, said he thought changes to prevailing teacher evaluation systems were necessary, but warned they may have caused as much harm as good.

“In our effort to move towards a better direction, were the costs larger than the benefits? That’s quite possible,” he said.

Research estimates how tenure and evaluation changes affected interest in teaching

The study looks back at a spate of laws prompted in part by the federal Race to the Top program. Between 2011 and 2016, the vast majority of states instituted stricter teacher evaluation rules tied to student test scores; a handful of states also eliminated or dramatically weakened teacher tenure.

The researchers attempted to isolate the effects of those laws on how many people in a given state wanted to become teachers. That would seem straightforward, and many others have highlighted national declines in enrollment in teacher training programs as evidence that policy changes have deterred would-be teachers. But it is actually quite tricky to point to cause and effect because so many other factors could make a difference, including the Great Recession, as well as other education policy changes, like the adoption of Common Core.

To get around this, the authors controlled for a variety of factors — including the state of the economy, teacher salary, and other policy reforms — and used the timing of states’ new laws to examine how the pool of teachers changed in response. No matter how they sliced the data, they said, the results held: after states adopted reforms, the number of new teaching licenses — that is, people eligible to teach in public schools — dropped substantially.

The magnitude was fairly substantial: a decline of about 15 percent for both evaluation and tenure reforms.

However, the two different types of changes followed different patterns: Evaluation reforms led to a gradual drop in teachers, while tenure removal led to a sharp decline, followed by a return to previous levels after a few years.

Grissom did point to one factor that might complicate the findings: charter schools, whose teachers don’t all have to be certified in some states.

“Charter schools are a small proportion of public schools, but it’s plausible that at least some of what they are seeing (in terms of fewer initial licenses) could be shifting of new teachers out of traditional publics into the charter sector,” Grissom wrote in an email. (Kraft pointed out that the vast majority of states require most or all charter teachers to be licensed.)

Using a separate data set, the researchers show that the evaluation and tenure changes also led to a significant decrease in the number of graduates from university-based teacher training programs, though these effects were more modest.

There was no evidence that the drops in enrollment were consistently concentrated in areas where there tend to be teacher surpluses, like elementary education or social studies. Evaluation reforms also didn’t affect the selectivity of the universities attended by teacher training graduates. On the other hand, weakening tenure did seem to screen out prospective teachers from lower-ranked schools — a potentially positive result — but they also appeared to reduce the number of would-be black teachers, which could hinder efforts to diversify the profession.

Although the study is in line with popular wisdom, it actually marks a shift from previous research, including Grissom’s, which has found little evidence that school accountability reforms like No Child Left Behind made teachers as a whole more dissatisfied or likely to quit.

The exact explanation for the findings is up for debate: It’s unclear how many teachers actually lost their jobs becauses of the new laws. Although the changes were prompted in large part because of concerns that too many teachers got high evaluation ratings, subsequent research by Kraft and Temple University’s Allison Gilmour found that high marks persisted in new evaluation systems, although in most states there was a small uptick in the share of teachers rated below average.

“Even if accountability reforms have no direct effect on job protections or satisfaction, they may still affect new labor supply if they affect the perception among potential entrants into the profession that teaching is a less secure or enjoyable career,” the latest paper says.

Were teacher evaluation and tenure changes worth the cost? It’s unclear

The study highlights the potential negative consequences of many states’ policy changes, and gives some credence to the concerns of many teachers and public school advocates that such laws were destined to dissapoint.

The findings suggest that schools have a smaller applicant pool of teachers to choose from, potentially leading to shortages in certain areas. The paper shows that the number of teaching licenses issues has dropped substantially since 2008, and, at least through 2016 has not recovered. Kraft said the actual impacts of the smaller supply will likely vary by state, school, and subject area.

“This is one of — not the only — but a contributing factor to the challenge of staffing hard-to-staff schools and hard-to-staff positions,” he said.

At the same time, Kraft said, the study is far from a full accounting of the impacts of evaluation and tenure changes. A number of studies focusing on specific districts point to benefits, including helping struggling teachers improve or replacing them with better ones. Other recent studies have shown that teacher turnover jumps in high-poverty schools in the wake of such changes, though the impact on students is unclear.

Kraft said it would be impossible to fully quantify the costs and benefits of the new laws, but again emphasized the effects likely varied: “These reforms played out very differently across states, and even more so across districts within states.”