The National Education Policy Center has renewed its call for states to curb the growth of full-time virtual schools until they can demonstrate dramatically improved academic results.

"Understanding and Improving Virtual Schools," released Wednesday, stems from an analysis of federal and state data sets for revenue, expenditures, and student performance across the 59 full-time virtual schools run by Herndon, Va.-based K12 Inc., the nation's largest for-profit online learning provider, according to a press release from NEPC, a nonprofit research organization based in Boulder, Colo.

Among the key conclusions of that analysis is that students in virtual schools run by K12 are performing worse academically and dropping out of courses at much higher rates than their brick-and-mortar counterparts.

For example, less than 28 percent of K12-run schools were found to meet the federal measure for Adequate Yearly Progress during the 2010-11 school year, compared with 52 percent of brick-and-mortar schools nationwide, the analysis found. However, about two-thirds of the students enrolled at K12 virtual schools had been at their full-time virtual schools for less than two full years, it showed.

"Computer-assisted learning has tremendous potential," said Gary Miron, the lead author of the study, an NEPC fellow, and a professor at Western Michigan University, in a press release. "But at present, our research shows that virtual schools such as those operated by K12 Inc. are not working effectively. States should not grow full-time virtual schools until they have evidence of success. Most immediately, we need to better understand why the performance of these schools suffers and how it can be improved."

[UPDATE: K12 Inc. has issued a statement in response disputing several of the study's findings, as it did to stories in the New York Times and other media outlets questioning the provider's methods in recent months.]

Ironically, while pushing to slow the growth of virtual schools run by K12 and others, the report also posits that virtual schools demand the creation of new accountability measures and funding structures that more accurately evaluate their unique aspects. Such recommendations have been supported by some virtual school advocates, including a structure where funding is based on course completions and not course enrollments, such as the Florida Virtual School's funding model.

The report is the latest in a series of work from the NEPC focusing a critical eye on the full-time virtual school movement. Like the others before it, this report pertains only to fully online solutions, and not to blended-learning models that mix virtual learning with face-to-face instruction.