TALLAHASSEE, Fla. — As a seventh-grader, Kelsey-Anne Hizer was getting mostly D's and F's and felt the teachers at her Ocala middle school were not giving her the help she needed.

But after switching to a virtual school for eighth grade, Kelsey-Anne is receiving more individual attention and making A's and B's. She's also enthusiastic about learning, even though she has never been in the same room as her teachers.

Kelsey-Anne became part of a growing national trend when she transferred to Orlando-based Florida Virtual School. Students get their lessons online and communicate with their teachers and each other through chat rooms, e-mail, telephone and instant messaging.

"It's more one-on-one than regular school," Kelsey-Anne said. "It's more they're there; they're listening."

Virtual learning is becoming ubiquitous at colleges and universities but remains in its infancy at the elementary and secondary level, where skeptics have questioned its cost and effect on children's socialization.

However, virtual schools are growing fast — at an annual rate of about 25 percent. There are 25 statewide or state-led programs and more than 170 virtual charter schools across the nation, according to the North American Council for Online Learning.

Estimates of elementary and secondary students taking virtual classes range from 500,000 to 1 million nationally compared to total public school enrollment of about 50 million.

Online learning is used as an alternative for summer school and for students who need remedial help, are disabled, being home schooled or suspended for behavioral problems. It also can help avoid overcrowding in traditional classrooms and provide courses that local schools, often rural or inner-city, do not offer.

Advocates say those niche functions are fine, but that virtual learning has almost unlimited potential. Many envision a blending of virtual and traditional learning.

"We hope that it becomes just another piece of our public schools' day rather than still this thing over here that we're all trying to figure out," said Julie Young, Florida Virtual's president and CEO.

Florida Virtual is one of the nation's oldest and largest online schools, with more than 55,000 students in Florida and around the world, most of them part-time. Its motto is "Any Time, Any Place, Any Path, Any Pace."

Struggling students such as Kelsey-Anne, who suffers from attention deficit disorder, can take more time to finish courses while those who are gifted can go at a faster speed.

Casey Hutcheson, 17, finished English and geometry online in the time it would have taken to complete just one of those courses at his regular high school in Tallahassee.