More and more school districts, as well as for-profit companies and nonprofit organizations, are offering Internet-based summer classes in core subjects, such as algebra and reading, and electives such as creative writing. In this article, the author discusses the growth of enrollment in online education for summer. The logistical ease of "anytime, anywhere" learning, the courses' relatively low cost to parents, and the increased need for students to meet state academic standards are some of the reasons online summer enrollment is continuing to rise, school and company officials say. The Orlando-based Florida Virtual School is on track to triple its student enrollment from 4,000 in 2004 to 12,000 in the following year, said Julie E. Young, the president of the state-sponsored public online school. Another 12,000 students remain on a waiting list.