Two University of North Carolina graduate students were curious: Were female school superintendents earning less than their male counterparts?

Considering longstanding gender pay gaps across the economy, they expected to find a disparity. And using data from Pennsylvania, they did. But they also turned up something else when they plugged in data about classroom teachers.

To their surprise, they found a small but notable gender pay gap for classroom teachers, who are usually paid based on set salary schedules that are designed in part to root out exactly those sorts of disparities.

Virtually no matter how the data is analyzed, female educators earn less than their male counterparts in Pennsylvania, and, according to a separate analysis released this year, Illinois.

Together, the two new studies illustrate how even the education field — a female-dominated one where many salaries aren’t open to negotiation — isn’t immune to the gender pay gap, at a time when strikes and walkouts mean extra attention is being paid to teachers’ wages.

The researchers say they’re not quite sure why it exists.

“That’s really the main question that is still unanswered,” said James Sadler, one of the researchers. “It’s something that we’re still still trying to figure out.”

While women made up 73 percent of classroom teachers in Pennsylvania, the study showed they accounted for just 44 percent of school principals and 35 percent of superintendents.

That probably explains a part of the pay gap for all educators, a group that includes both classroom teachers and higher-paid administrators. (Nationally, women make up 77 percent of the public school teaching force but 54 percent of principals; just one in five superintendents in the 100 largest school districts have been women over the last decade and a half.)

Read the full article about the pay gap in the education field by Matt Barnum at Chalkbeat.