A new study from the University of Arkansas finds that crime rates among students in private school voucher programs are lower than those among students who attend traditional public schools.

The research,  conducted by doctoral student Corey DeAngelis and professor Patrick Wolf, scrutinizes the Milwaukee Parental Choice Program — the longest standing school choice law in the United States.

Not only did the study show that crime rates drop among voucher students, it also indicated a continued decline in criminal behavior during a student’s long-term enrollment in the program.

“We conclude,” the paper says, “that merely being exposed to private schooling for a short time through a voucher program may not have a significant impact on criminal activity, though persistently attending a private school through a voucher program can decrease subsequent criminal activity, especially for males.”

The MPCP is similar to North Carolina’s Opportunity Scholarship Program, which was signed into law in 2013 and allows financially challenged families up to $4,200 annually to send their child to private school.

The Tar Heel state’s voucher program was subjected to a host of legal challenges regarding the use of public tax dollars to fund private education prior to July 2015, when the North Carolina Supreme Court ruled the law constitutional.

The program now has awarded more than 2,500 children vouchers to attend private schools during the 2015-16 school year, and is on more solid footing with parents who are looking for reliable education options, says Terry Stoops, director of research and education studies at the John Locke Foundation. But though the voucher program is moving forward, challenges remain.

“There is still some alignment necessary between private schools and the State Education Assistance Authority,” Stoops said. “And these are issues that can be worked out with minor changes to the law, or minor changes put in place by the SEAA that makes it easier for parents and private schools to accommodate the scholarship program.”

Wisconsin’s program has faced problems of its own, with opponents of MPCP trying to paint the University of Arkansas’ recent study as biased and inaccurate.

Wolf rebuts such claims, stating that the research is accurate, and pointing to previous studies that have included information about school choice failures as well as successes.

“If I’m a researcher biased in favor of vouchers,” the Milwaukee Journal-Sentinel quotes him as saying, “I’m not very good at it.”

“This research shows the important correlation between a receiving great education and keeping children and our communities safe,” Kevin Chavous, executive counsel for the American Federation for Children, said in a statement. “We hope people look at this paper and see the broad positive impact of educational choice and a quality learning environment.”

Read the full study here: The School Choice Voucher: A “Get Out of Jail” Card?