STANFORD, Calif. – Charter school students outpaced their peers in traditional public schools in reading and made comparable gains in math over the past few years, according to a national study released Tuesday.

The National Charter School Study by the Center for Research on Education Outcomes (CREDO) at Stanford University shows slow but steady academic improvement among charter school students since 2009.

According to the study, “The average charter school student now gains an additional 8 days of learning each year in reading, compared to the loss of 7 days each year reported in 2009.”

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CREDO analyzed student performance from 25 states, the District of Columbia and New York City, which was considered separate from upstate New York due to its vast number of students.

An estimated 2.3 million students were enrolled in charter schools during the 2012-13 school year, an 80 percent increase from 2009.

“The results reveal that the charter school sector is getting better on average and that charter schools are benefiting low-income, disadvantaged and special-education students,” CREDO Director Margaret Raymond said, according to the Santa Maria Times.

Black students, students in poverty and English language learners saw the greatest gains in learning in both reading and math.

“Black students in poverty who attend charter schools gain an additional 29 days of learning in reading and 36 days in math over their [traditional public school] counterparts,” the study stated.

American Federation of Teachers president Randi Weingarten was quoted by the Times as saying the findings show that charter schools have failed to live up to “the leaps and bounds that were promised” in student performance.

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“We should use the CREDO findings as an opportunity to pause and ask ourselves why we keep pitting charter schools against neighborhood public schools – a strategy that has created little more than a disruptive churn,” Weingarten said.

But Raymond believes such improvement should not be overlooked.

“We think that level of improvement is really noteworthy given that it’s only been a few years,” Raymond said.

Raymond said the gains were partially attributed to the closure of underperforming schools.

The report calls closing low-performing schools “the strongest tool available to ensure quality across the sector.”