MILWAUKEE (AP) -- State auditors on Wednesday confirmed a report that found little difference in test scores between students in Milwaukee's school-voucher program and those in the city's public schools.

Wisconsin lawmakers had asked the state Legislative Audit Bureau to evaluate a study, conducted by privately funded education researchers, that analyzed test scores from both groups of students. The study had found no significant difference, a conclusion that state auditors also reached.

The researchers studied the Milwaukee Parental Choice Program, a voucher program that allows low-income children in Milwaukee to attend private schools at taxpayers' expense. The two-year budget signed by Gov. Scott Walker in June repealed the enrollment limit for voucher schools in Milwaukee and expanded vouchers to schools in suburban Milwaukee and Racine.

Supporters say the voucher option helps students whose only alternative might be a substandard public school, and gives them more control over their own education.

However, opponents say the voucher program hasn't proven any more effective at raising students' test scores. Critics, including Wisconsin state superintendent Tony Evers, have also opposed expanding the program, arguing that lawmakers should focus on improving achievement of all Wisconsin school children before using taxpayer money to bolster vouchers.

The latest report could provide fodder for both sides.

The researchers had compared math and reading scores between both sets of students, and found only slight differences.

State auditors evaluated the numbers a little differently. For example, unlike the researchers, the auditors omitted from their analysis any students who transferred between a public school and voucher school during the five-year period covered by the study.

Even so, the auditors arrived at a similar result: that the differences between the test scores weren't statistically significant.

Mike Ford of School Choice Wisconsin, a group that supports voucher programs, said the numbers should silence critics who think voucher schools aren't as robust as public schools.

"This basically confirms that School Choice knows what it's doing," he said.

But the Wisconsin Association of School Boards said it was ridiculous to divert taxpayer money toward schools that perform no better than public schools.

Spending all that money on private schools "without any evidence of improvement is harming all the public schools in Wisconsin," said Joe Quick, a spokesman for the association.

Wednesday's report follows a similar but unrelated study by the Wisconsin Department of Public Instruction that came out in March.

That DPI study found that students at Milwaukee's public schools outperformed voucher students. However, that study looked at data from a single year, while the research reviewed by the audit bureau is part of a five-year study. The DPI study also looked at the 2010-11 school year, while the researchers evaluated scores up to the previous year.