by Athena Jones, CNN
CHANTILLY, VIRGINIA (CNN) - It's a Tuesday morning in January, and seventh-grader Katerina Christhilf is learning algebra. But it's no ordinary class. This one takes place entirely online, led by a teacher a few miles away.
As part of her training to become a ballerina, Katerina takes dance lessons four times a week, including up to eight hours on Fridays. All that training makes it hard to go to a conventional school, so she takes science, literature, composition, vocabulary, history, music, art and French - a full course-load - from the comfort of her home, through Virginia Virtual Academy, a program run by K12 Inc. that began operating in the state in 2009.
"Ballet is really important to me and it's usually in the mornings, so if I went to school I would only be able to go on the weekends," Katerina explained. "Sometimes I'll study in the morning and I'll do a few classes and then I'll go to ballet for maybe like three or four hours and I'll come back home and I'll do some more."
Katerina is one of a growing number of students who go to school online full time. About a quarter of a million students in kindergarten through 12th grade were enrolled in full-time online schools last year, according to the International Association for K-12 Online Learning, a 25% increase over the previous year. Some parents choose these schools because their children are struggling in traditional schools; others do so for their flexible schedules.
But as the number of students learning online full time has grown, so have questions about the effectiveness of that approach.