Assigning elementary teachers to teach only their best subjects, also known as "teacher specialization," holds a lot of appeal—but new research shows the practice has surprisingly negative impacts on student learning. As this research follows on the heels of other research finding similar results, it may be time for schools to consider phasing this practice out.

In many ways, the negative results are counterintuitive. Instead of the standard elementary model of having every teacher teach all core subjects, why not allow the 4th-grade teachers who see the greatest student achievement gains in reading to teach reading to all 4th-graders? You can capitalize on teachers' comparative advantages! Surely it would also allow districts to streamline professional development. In fact, it likely would reduce teachers' stress as they'd only have one subject area for which they need to prep.

But, as with many things in life, it's not that straightforward.

This most recent study, looking at more than 15,000 math teachers and 17,000 reading teachers across Indiana, shows that teacher specialization in the elementary grades leads to lower teaching effectiveness. Specifically, when the researchers compared the effectiveness of the same teachers in years when they did specialize (i.e. taught only one or two subjects) with the years they did not specialize (i.e. taught 3+ subjects), they found that their student learning gains declined significantly in both reading and math.

To make matters worse, the kids who typically struggle in school—those who already achieve at lower levels, who are eligible for free or reduced-price lunch, English Language Learners, and students enrolled in special ed—were disproportionately impacted. While all students' reading and math scores on Indiana's statewide assessment declined when taught by specialized teachers, these subpopulations saw an even greater negative impact.

One possible—but incorrect—explanation for the surprising results is that Indiana teachers who have lower value-added scores or are labeled by the Indiana Department of Education as "not highly qualified" are more likely to specialize in elementary grades. Of course student scores will decrease in a certain subject area if a teacher who is deemed less effective teaches it. But these findings show that these already less effective teachers become even less effective when they specialize.

And it's important to note that the negative impact on student achievement in this study is echoed by others, including one in North Carolina and one in Texas, where teachers who were considered highly effective (as measured by value-added scores and principal evaluations) were more likely to be specialists.

While none of these three studies can explain these results, they all posit the same reason: weakened student-teacher relationships. Plenty of research shows that teachers' knowledge of their students and the ability to tailor instruction based on this knowledge is critical to learning, especially in the elementary grades.

For all of its allure, teacher specialization in elementary grades may be a practice that needs to end, or at least be conducted more sparingly.

This content was originally published on the AASPA Blog on January 28, 2022.