An article yesterday about a comparison of standardized test scores between African American students in D.C. public and Catholic schools incorrectly reported what number to call for a copy of the study. The number is 202-546-4400. (Published 10/08/1999)

African American students at D.C. Catholic schools significantly outscored their public school counterparts on a national math exam, even adjusting for socioeconomic factors, according to a new study by a think tank that supports the use of tax-funded school vouchers.

The study by the Heritage Foundation showed that the gap between black youngsters at Catholic and public schools in the District widened over time, from 6.5 percentage points for fourth-graders to 8.3 percentage points for eighth-graders. The test, the National Assessment of Educational Progress math exam, is administered every four years to a sample of students nationwide. For the study, only the results for the District were analyzed.

Researchers adjusted for differences in family income and other indicators of academic success: two-parent families, educated parents, reading materials in the home. They found that none of those variables affected scores as much as whether a child attended Catholic school--a fact that will probably be trumpeted by supporters of using public dollars to pay private school tuition.

"All the study really says is, you can't just say it's differences in children's backgrounds," said Stuart Butler, a foundation vice president. "The bottom line that we would say to the [public] school system is maybe they ought to look at why the Catholic schools" do better.

D.C. School Superintendent Arlene Ackerman said through a spokeswoman that the study was "sort of like comparing apples to oranges," because Catholic schools can impose discipline and demand family involvement in ways that public schools cannot.

"They operate under different guidelines and policies," said Devonya Smith, Ackerman's executive assistant. "We accept all children, and Catholic schools have leeway."

Lawrence Callahan, the superintendent of schools for the Archdiocese of Washington, dismissed such reasoning as "an old myth." He said that the city's archdiocesan schools, which last year enrolled nearly 5,300 students, accept everyone they have space for and rarely ask a student to leave.

"We want to serve every family that desires a Catholic education," he said. "It does require commitment on the part of the family. . . . There is an expectation that they're involved in the school."

Although the Heritage study is the first to compare test scores for students in a major U.S. city, other research also has found a distinct difference in achievement between public and parochial school students nationwide.

Proponents of public schools oppose vouchers because they believe they will strip resources and strong students from the public schools. They say that even if other demographic factors are similar, a family's decision to choose a Catholic school implies a commitment to education that is not present for all public school families.

Catholic schools also generally offer more structure, with school uniforms, daily prayer and strict behavior codes. Classes are often bigger than in public schools--they can have 35 students or more--and teachers and principals are paid much less than are their public school counterparts.

Enrollment in archdiocesan schools in the city jumped nearly 5 percent last school year, in large part because hundreds of students received partial scholarships from private organizations.

Supporters of publicly funded vouchers--which Republican presidential candidate George W. Bush has said he would offer to children in failing schools--say thousands more D.C. children would opt for private or parochial school if they had access to such funds.

Tax-funded voucher programs in Cleveland, Milwaukee and Florida have come under court challenge, in part because so many recipients use the money to attend religious schools. Congressional Republicans for years have tried unsuccessfully to force vouchers on the District, despite opposition from city leaders and the White House.

The complete study can be obtained by calling 202-544-4400 or viewed on the foundation's Web site,