Years of research show that principals can significantly impact student achievement. Now, a major new study quantifies just how much difference an effective principal can make.
Replacing a below-average principal with someone in the above-average category—for example, a principal in the bottom 25th percentile on effectiveness with one in the 75th percentile or above—can add the equivalent of 2.9 more months of learning in math and 2.7 more months of learning in reading during a single school year, according to the report released by the Wallace Foundation Tuesday.
Similar studies on teachers have shown that making those adjustment in teaching staff—replacing a teacher in the lowest 25th percentile with one in the 75th percentile—can add the equivalent of 3.7 months of learning in math and 3.8 months of learning in reading.
Those findings came from a review of six rigorous longitudinal studies using data on more than 22,000 principals in the Miami-Dade and Chicago districts, as well as statewide data on principals in Texas, Pennsylvania, North Carolina, and Tennessee.
It’s part of a larger in-depth review of hundreds of studies and research on principals over two decades.
The authors included a few caveats on the academic findings. The studies are limited to a handful of states, and the principals led only elementary and middle schools. It’s unclear whether the effects would be similar in high schools, which are generally organized and run differently from elementary schools. They urged additional study to help fill in those gaps.
The report’s authors said that principals have a far more expansive effect on students because their impact is schoolwide, while the teacher’s effect may be limited to their class.
“Principals’ effect is not as large as teachers’, on average,” said Jason Grissom, a professor of public policy and education at Vanderbilt University and one of the authors of the study. “But the principal’s effect is realized across the school, whereas a teacher’s effect is realized in his classroom. …The [principal’s] impact is big in magnitude, but also big in scope.”
But it’s not an either-or proposition: principals or teachers, Grissom said.
That’s because the main ways that principals affect students are through teachers and by creating school environments that are ripe for learning to take place.
If anything, the report notes, previous research did not fully capture the breadth of principals’ effect on student outcomes. The results extend beyond academics, with effects on student attendance and teacher turnover, according to the authors.
“Indeed, it is difficult to envision an investment in K–12 education with a higher ceiling on its potential return than improving school leadership,” the authors noted.
The new report, “How Principals Affect Students and Schools: A Systematic Synthesis of Two Decades of Research,” is the most in-depth review of research on school leadership since Kenneth Leithwood’s seminal publication in 2004 made the case that principals were only second to teachers among in-school factors that affect student learning.
Effective principals are skilled in instruction, people, and organizations
The report digs into three broad aspects of today’s school leaders: their impact on student outcomes; who they are, including demographic profiles; and the skills and behaviors that effective principals display.
To answer the question of the impact on student achievement, Grissom and his colleagues, Anna J. Egalite, an associate professor at NC State, and Constance A. Lindsay, an assistant professor at the University of North Carolina at Chapel Hill, dug into decades of research.
Principals’ effect is not as large as teachers', on average, but the principal's effect is realized across the school, whereas a teacher’s effect is realized in his classroom.
Leithwood’s study, like the new one, was commissioned by the Wallace Foundation, and it ushered in a reorientation in the role of principals as instructional leaders, with a new emphasis on developing their instructional capacity over the managerial aspects of the job.
But while the new report does not discount instructional leadership, it makes the argument that effective principals do much more than focus on instructional practices—and that there are specific instructional practices that make a difference. (The authors actually prefer the term “instructionally-focused interactions with teachers” to more clearly emphasize that these are activities related to helping teachers improve.)
Effective principals are skilled in instruction, people, and organizations. And they also engage in a series of behaviors that set them apart from others, the authors learned from their in-depth reviews of 219 studies, pulled from a larger group of more than 4,800.
In addition to the instructional role—which includes things like teacher-evaluations, coaching, and developing an academic plan and vision—effective principals also focus on strategies that build a climate conducive to learning (teamwork, trust, and continuous improvement); foster collaborative learning communities; and manage personnel and school resources, according to the report.
“The education field has tended in recent years to focus on developing principals’ instructional skills as the key to increasing student learning, but this synthesis suggests that effective principals actually use a much broader toolbox,” Egalite said in a statement.
Grissom does not envision the pendulum swinging away from instructional leadership with this new report.
However, he favors a more holistic understanding of the principals’ job and how effective school leaders impact both teachers and students. That would help districts, states, preparation programs, and policymakers think strategically about developing future school leaders, professional-learning programs, and how universities design programs and recruit candidates for them. It’s also good information in targeting investments to help principals build and strengthen those additional skills, he said.
“Yes, there are instructional leadership components, but these other pieces are important, too” Grissom said.
Principals’ race and ethnicity affect performance, teacher retention
The new report also looks at the demographics of the profession over time. More women and more people of color have entered the profession, with women making up 54 percent of school leaders, according to federal data. That’s up from 25 percent in 1988, according to the report. But that growing diversity has not kept pace with the demographics of students in public schools, where non-white students are now the majority.
And there’s a particularly yawning gap between the percentage of Hispanic principals and Hispanic student enrollment. According to federal data, only 9 percent of school leaders were Hispanic in the 2017-18 school year, while Hispanic students made up about 28 percent of public school enrollment in fall 2020.
That matters, Grissom said.
An emerging body of research suggests that the race and ethnicity of the principal may play a role in student outcomes and teacher retention. Grissom previously examined data in Tennessee and Missouri and found that the number of Black teachers hired increased when schools were led by Black principals, and that even when Black principals did not hire Black teachers, Black students’ math scores improved.
The effects go beyond academics and can include higher enrollments of students of color in advanced courses and better attendance, as Grissom and his colleagues found in a 2004 study of Latinx students in Texas who attended schools helmed by Latinx principals.
“The outcomes for kids seem to be at least, in part, a function of who is in the principal’s office,” Grissom said.
Plus, Grissom said, principals who are approaching the job with a concern for diverse needs of all their students are doing some things differently—and those approaches are making a difference for students academically.
While researchers can document the practices that these principals engage in, they can’t yet draw a clear line between those efforts and the outcomes, Grissom said.
“They are engaging in strategies that have all students in mind,” he said. “These are principals who are celebrating diversity; these are principals who are trying to communicate high expectations for all students; principals who are trying to build opportunities, not just for the teaching staff, but also for families in the community to work together to meet students’ needs. Their behaviors are different.”
The authors argue that districts and leadership preparation programs should prioritize recruiting, hiring, and supporting principals of color to reflect the student enrollment and that equity should be a key component of the work that principals do.
They also make the case that effective principals need to be more equitably distributed in school systems, especially among schools serving students of color, low-income families, and other marginalized communities. And there’s need for additional research. Leithwood’s 2004 study led to focus on the principalship as a key lever for change in schools.
Grissom is hoping that this report will also similarly underscore the importance of school leadership and that it’s a role that deserves more attention and investment at the district, state, and federal levels.
He hopes it will also lead to sustained efforts to ensure that schools have effective principals at the helm, given the huge difference they can make.
“Principals are a high-leverage action for school improvement,” Grissom said. “I think we were able to document that and quantify that to some extent. So the need for investment is a big piece.”
