Six-year-old Eric Moll is excited about his new school. He gets to do advanced work, much of it online. Best of all, he can bring his rainbow-colored bird, Dexter, to class and stay in his pajamas as long as he wants.

His mother, Lori Moll, loves the school, too. In addition to overseeing Eric's learning at home, she chooses his lessons and receives a computer, a year's worth of classroom supplies and access to a teacher-mentor -- all for free.

Eric and his brother, Lorin, 9, attend class in what used to be their play area next to the dining room. They are enrolled in a new educational concept: a cyber charter school.

Such schools, like the charter schools made of bricks and mortar, are government-funded and independent of most state and local education rules. The difference is that students at cyber charter schools stay at home and connect to their lessons and teachers via computers.

Combining the flexibility of home-schooling with the structure of public schools, the cyber charters are fast becoming a popular option for gifted and disabled students who need special attention. And increasingly, they are filling a market niche for parents who want to home-school their children but lack the expertise to teach or the money for materials, equipment and textbooks.

Started about three years ago, cyber charter schools, or virtual charter schools, are operating in 12 states, including California, Wisconsin, Ohio, Pennsylvania, Colorado and Alaska.

About 16,000 students are enrolled in 50 such schools that offer elementary and high school curricula, nearly double the number last year.

Yet opposition to such schools is mounting. Concerns about lax academic standards and financial accountability at some cyber charter schools have prompted lawmakers in California, Pennsylvania and Ohio to clamp down, taking away some of the freedom the schools have. In Pennsylvania, more than 100 school districts have filed lawsuits to stop cyber charters, arguing that they siphon money from other public schools.

And home-school advocates, who eschew the values and bureaucracy of government schools, consider the cyber charters a threat. Some advocacy groups are warning that cyber charter schools could bring more government scrutiny to home-schoolers.

"Cyber charter schools are tapping into the understandable frustration that home-schoolers have in paying thousands of dollars in property taxes and not getting a nickel for their kids' education," said Thomas Washburne, director of the National Center for Home Education at the Home School Legal Defense Association in Washington. "Once we accept government money, the more likely regulation of home education will come."

After Moll was unable to find a public or private school to meet the needs of her two gifted sons, she explored home-schooling. But she was overwhelmed by the prospect of piecing together daily lessons from an array of curricula she saw at a home-schooling convention and intimidated by the idea of teaching them herself.

Instead, she enrolled the boys in the new California Virtual Academies, which have charters to operate home-based cyber schools in about 30 counties in the state. The daily lessons -- along with computers, software, books, art supplies, maps, math toys and more -- are provided by K12 Inc. The company, established by William J. Bennett, education secretary under President Ronald Reagan, provides curricula for online schools nationwide.

Whenever she gets stuck, Moll can e-mail or call Brenda Friedl, a certified teacher at the school who works at a computer in her own home.

Moll is required by state attendance rules to log the number of hours that Eric and Lorin spend on each subject. But she and the boys are free to work at their own pace, devising a schedule that best meets their needs.

"I couldn't have done this myself as extensively," Moll said. "We're getting something for the tax dollars we're paying. I never got anything before."

At a time when state public education money is getting tighter, school districts in several states are grumbling about cyber charter schools, regarding them as an effort to subsidize parents who home-school their children.

Charter school laws were established nationwide 10 years ago in an effort to introduce innovation into public education with government-funded, privately run new schools untethered to most state and local education rules. A regular public school loses the state's per-pupil allocation of about $5,000 whenever a student transfers to a charter school.

In some states, districts also pay their own $5,000 or so per-pupil cost to the charter.

The debate over cyber charter schools centers on the contention that they are not entitled to the full per-pupil allotment because they do not have infrastructure expenditures for buildings, grounds, maintenance, janitors and buses.

Moreover, teachers unions and school boards have argued to lawmakers that more accountability is needed, pointing out instances of mismanagement at several such schools.

David Mowery, the superintendent of the Gettysburg Area School District in Pennsylvania, said he discovered last year that Einstein Cyber School was billing the school system for a student who falsified his address. The student did not live in the district, but in Dallas.

Einstein's charter eventually was revoked and the school has appealed, according to the Pennsylvania Department of Education.

Such concerns have prompted Gettysburg and more than 100 other Pennsylvania school districts to withhold their subsidies for students who transferred to cyber schools and to assert in lawsuits that the schools violate the state's Constitution.

The California Legislature passed a law last year that reduces the cyber charters' allotment if they do not spend 50 percent of their public revenue on salaries for certified teachers. The Ohio Legislature, responding to a state audit showing that the Electronic Classroom of Tomorrow billed the state for some students who were not enrolled and did not provide computers for some who were, is considering a measure that would strengthen the requirement that schools verify their data.

"There are some crappy cyber schools setting up, and we are as interested as the states are in seeing that they don't survive," Bennett said.

"The more scrutiny, the better," he added. "Nothing will put us out of business faster than bad cyber charter schools."

A white board in the dining room of Anastasia Corey's home in Camarillo, Calif., says, "Welcome to home school." At a computer hutch in the living room, Anastasia, 11, reviewed a lesson on amphibians, staring at colorful pictures of frogs on the screen.

Anastasia, recently adopted from Russia, is learning English. Her parents moved her to California Virtual Academies from a private school, which had her in a third-grade classroom and a first-grade reading program.

The cyber charter school "gives me everything I need, and I can tailor it to her learning style. She can do a lot on her own," said Susie Corey, Anastasia's mother. "This was a huge answer to prayer."