Louisiana teachers in traditional public schools are nearly three times more likely to be chronically absent than charter school teachers, according to a national study released Tuesday.

A total of 27.9 percent of teachers in traditional schools here missed more than 10 days of work for sick or personal leave compared to 10 percent by charter school educators, a 37-page report by the Thomas B. Fordham Institute says.

"How can anyone expect students to learn when their teachers are absent?" the authors of the study asked.

Education groups disputed the findings, and said annual leave for teachers is set by state law.

They also questioned the report's view that generous collective bargaining agreements between teacher unions and school boards are the key reason for the difference with less unionized charter schools.

Collective bargaining agreements are rare in Louisiana's 69 school districts.

The Louisiana Federation of Teachers, one of the state's two teacher unions, has collective bargaining agreements in St. Tammany Parish for non-administrative workers and teachers only in Jefferson Parish.

The Louisiana Association of Educators, the other union, has agreements in the Vermilion, St. John, St. Helena and St. Bernard school districts.

The Fordham Institute is an education research group in Washington, D.C.

It has criticized traditional public school practices in previous reports.

The findings for Louisiana mirror the national rate, with 28.3 percent of teachers in traditional public schools listed as chronically absent compared to 10.3 percent in charter schools, with are public schools run by non-governmental boards.

More than 700,000 students attend the state's roughly 1,300 traditional public schools.

About 80,000 students attend Louisiana's 145 charter schools.

The report said that, on average, American workers are entitled to eight paid sick days per year and only 40 percent get paid personal leave.

Louisiana gives teachers 10 sick or emergency days per year, and two can be used as personal days with 24 hours notice.

LFT President Larry Carter, who had not read the study, said Tuesday that chronic absences by public school teachers is not an issue.

Carter said a variety of factors could help explain differences in the absence rate of traditional and charter school teachers. Many charter school teachers are younger, less likely to need time off for children or spouses and tend to leave the profession quicker, he said.

The Fordham review focused on the 2013-14 school year.

David Griffiths, senior policy associate and author of the study, said it is hard to understand why Louisiana's figures echo national trends even though collective bargaining units are rare in the state's public school districts.

Griffiths said the state's 10-day sick leave policy could be a factor since it mirrors some union agreements elsewhere.

"That is fairly generous,'' he said.

The report said its definition of chronically absent teachers – missing more than 10 days per year for sick or personal leave – was taken from the definition used by the U.S. Department of Education's Office of Civil Rights.

Asked about the report, state Superintendent of Education John White said in a statement, "The vast majority of educators are diligently present in school and work long hours to serve their students."

"Though it is rare, if a teacher is not routinely in their classroom, it disrespects not only their students but the professionals who work alongside them," White said.

Caroline Roemer, executive director of the Louisiana Association of Public Charter Schools, said she had not read the report.

School districts can report teacher absence figures to the state Department of Education but it is voluntary and most do not.

Follow Will Sentell on Twitter, @WillSentell.