For three years, private schools participating the Alabama Accountability Act — the state’s much-debated school choice program — have been collecting test data to measure their students’ performance.

But when that data is released in September, it won’t be broken down on a school-by-school basis — a stark contrast from the testing regime at public schools, which will soon get A-through-F grades based on standardized test scores.

“We’re trying to compare kids in the program to comparable kids who are in public schools,” said Joan Barth, a faculty member at the University of Alabama’s Institute for Social Science Research, which is crunching the Accountability Act test numbers.

Passed by the Legislature in 2013, the Accountability Act gives tax credits to parents who pull their children out of “failing” public schools —  the lowest performers on state tests — and place their children in private schools. Another, more often-used provision of the bill gives an income tax credit to companies and people who donate to scholarship programs that let low-income students anywhere in the state go to a private school.

Proponents of the Accountability Act say that by giving parents a choice of public or private school, regardless of income, they’re holding schools accountable for results. Opponents say the law it saps public schools of resources while providing little help to students.

Lawmakers set aside $25 million for tax breaks for the program in the Accountability Act’s first year; as of June 30, about 4,000 studentsare getting scholarships through the program, according to reports filed by scholarship-granting agencies.

Testing was always part of the design of the Accountability Act. Participating public schools were supposed to test scholarship students using one of the nation’s more widely used standardized tests, and the results of the tests were supposed to be reported to the public in the third year of testing.

That report is due Sept. 1, but state officials and researchers say that means we won’t get school-by-school accounts of test performance, comparable to the state’s annual reports on the progress of public schools.

“If they requested that we do it that way, we probably could,” said Barth, the researcher.

Only the test scores of scholarship recipients are collected, which means a school-by-school report could run afoul of student privacy law.

“For some schools, there might be only one scholarship recipient,” Barth said. “You don’t want a child to be identified in the results.”

Instead, Barth said, the September study will look at the test scores of certain types of students – she used the example of a white, male fifth-grader – compared to students in public schools with similar demographic backgrounds.

That study, too, faces challenges. Public schools all use the same set of standardized tests, created by the company that administers the ACT college entrance exam. There are at least five different standardized tests in wide use by private schools around the country — making apples-to-apples comparisons more tricky.

A lack of testing data has long been a sticking point for the Accountability Act’s most vocal critics.

“The farther we get into this, the more we see that there’s not any real accountability in it,” education blogger Larry Lee, an opponent of the act, told The Star last week.

Sen. Del Marsh, R-Anniston, who wrote both the Accountability Act and a 2015 revision to the act, said it’s too early to criticize a study that hasn’t yet been released.

“Let’s at least wait until the numbers are out in September,” Marsh said.

Under the 2013 version of the law, schools were supposed to begin reporting test data in the first year of the scholarships. When The Star checked with schools in early 2015, none said they’d been asked for data.

In a revised version of the Accountability Act, passed a few months after The Star’s report, schools are required to report their data to scholarship-granting organizations, which then turn it over to researchers for study. Only the final report goes to the state government.

If the scores were reported directly to the Department of Revenue, which administers the Accountability Act, they might be subject to disclosure under the state’s open records laws.

The department hasn’t received raw test data, spokesman Frank Miles said last week.

Public schools release school-by-school test scores annually, a practice that has been in place since at least the 1990s. Lawmakers in 2012 voted to include a schoolwide grade of A through F, based on those annual scores.

State school officials say those grades will be posted for the first time in December.

Capitol & statewide reporter Tim Lockette: 256-294-4193. On Twitter @TLockette_Star.