Online public schools, where students as young as kindergartners log on from home to take classes, don't make the grade, according to a study released Friday.

Less than a third of the "virtual" schools managed by for-profit companies made adequate progress toward meeting state standards last year, compared with about half of all public schools, according to the report from the National Education Policy Center at the University of Colorado at Boulder.

The findings demonstrate that online public schools, which educate more than 200,000 students nationwide, don't have the results to justify their growth, said Gary Miron, lead author of the study and a professor at Western Michigan University. K12 Inc., part-owned by billionaire Michael Milken, and Pearson's Connections Academy are the biggest operators of Internet-based charter schools - privately run public schools.

"I don't think students are being well-served," Miron said. "I don't think taxpayers are being well- served."

The study's results may reflect the kinds of students flocking to online public schools - such as those who have fallen behind in high school - more than the quality of instruction, said Susan Patrick, president of the International Association for K-12 Online Learning, a nonprofit advocacy and research group in Vienna, Va.

"The kids enrolling in online schools needed something other than the traditional system," Patrick said. "It can be a great option."

The study looked at both for-profit and nonprofit companies that specialize in running charter schools. Researchers determined how many of the schools overseen by these companies were making "adequate yearly progress" toward passing state standardized reading and math tests under the federal No Child Left Behind Law.

Twenty-seven percent of virtual charter schools run by for-profit companies showed satisfactory progress, down from 30 percent the year before, the study found. For-profit companies managed almost all of the Internet schools in the study.

The National Education Policy Center received funding for the study from the American Federation of Teachers, which says on its website that charter schools should be not-for-profit and open to teachers unions.

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