Voucher participation has climbed during the past 10 years, and those who benefit the most are African-American students who attend Catholic schools, according to a recent study.

The study, “The Education Gap: Vouchers and Urban Schools,” published by the Brookings Institution, noted that most students who use vouchers have chosen to attend religious schools.

It also showed that test scores for African-Americans who use vouchers jumped 3% in first grade and doubled that gain the following year.

The study also showed that, although Catholic schools account for half of private schools, they make up more than that proportion of schools selected by voucher students. More than two-thirds of New York City students using vouchers choose Catholic schools. In Dayton, Ohio, more than half the students choose Catholic schools, and in Washington nearly half do.

During a recent conference in Washington sponsored by the Brookings Institution, two of the study's authors also pointed out other details about private schools.

For example, private-school students overwhelmingly are more likely to go to church than students from public schools, said William Howell, a professor at the University of Wisconsin at Madison.

“Sixty-eight percent of private-school students attend religious services,” said the professor, one of four authors of the voucher study. “Thirty-eight percent of public school students attend religious services.”

Paul Peterson, director of the Program on Education Policy and Governance at Harvard University in Cambridge, Mass., also pointed out that Catholic schools educate students at half the cost of public institutions.

The study's authors said that, in the past decade, the number of students using vouchers to attend private schools climbed from about 5,000 to more than 60,000 and that nearly 50,000 of these students currently participate in 68 privately funded voucher programs and another 12,000 participate in three publicly funded programs.

In Dayton, New York and Washington, the three cities studied for the report, voucher programs are funded from private foundations.

The key distinction between privately and publicly funded voucher programs is that publicly funded vouchers expect no contributions on the part of parents while privately funded vouchers do.

The researchers concluded that this cost drives many parents to opt for charter schools, which have been gaining in popularity.

A weakness of the voucher program, according to Allan Krueger, an economist from Princeton University in Princeton, N.J., is that while students in the first and second grade post higher test scores than their public school counterparts, those in the third and fourth grades do not.

Krueger, pointing to a study of vouchers by the Mathematical Policy Institute, said that “average test scores in math went down for the group in the voucher program.”

At the Brookings conference, he said he finds the concept of vouchers “interesting,” but pointed to smaller class sizes as an alternative to achieve educational gains.

Peterson responded saying ideas about smaller class sizes and more spending have been tried for 30 years and have failed to produce results.