This fall, David Kayler plans to challenge himself like never before. As a 10th-grader at a rural North Carolina high school, his courses will include 11th-grade chemistry and honors algebra. When he gets home, he will attend classes at his other school -- in cyberspace.

For many of today's gifted students, honors programs at their own schools aren't challenging enough anymore. Like 15-year-old David, they are signing up for online courses offered by such colleges as Stanford University, Johns Hopkins University and the University of Missouri. David, for example, will write short fiction for an online class at Duke University.

These online courses offer classes mainly in advanced math and English, but subjects such as history, philosophy and anatomy also are offered. Programs are available for students of all ages, kindergarten through 12th grade, and some courses for high-school students follow college freshmen curricula.

Not only do these classes bring in extra revenue, but for universities competing for the nation's brightest students, online programs are a useful tool for identifying and attracting them. Colleges keep track of students in their online programs and later mail them brochures highlighting their undergraduate programs. Participating may even give students a leg up in gaining admission to popular colleges.

Increasingly, high school counselors, especially in rural schools where resources for gifted students often are limited, have begun combing through student records and encouraging top performers to apply for online courses. Some counselors go so far as to submit grades directly to universities, which regularly host regional "talent searches" where students are invited to take standardized tests to see if they qualify for the courses.

Courses cost from $120 to more than $1,000 each, and typically last a semester, although some stretch out over two semesters.

Some of the courses offer credit toward high-school graduation requirements, but because local and state educational requirements vary, schools must decide how much credit, if any, a student may receive.

Online classes typically have 20 to 40 students. They usually meet at least once a week in teacher-moderated online chat rooms, and the participants sometimes speak with one another using headsets and microphones. Homework is downloaded and, once completed, either submitted to the teacher via email or posted to an online message board so that classmates can critique each other's work. Teachers usually assign real textbooks for students to read, although increasingly CD-ROMs and scholarly Web sites also are used.

Before the Internet, gifted high-school students could attend classes at nearby universities or send away for college-level books and CD-ROMs. Now, the availability of online classes is leading to greater interest in gifted-student programs by students, particularly those in rural areas, says Patricia Wallace, author of "Psychology of the Internet" and director of the Center for Talented Youth at Johns Hopkins.

Stanford began offering classes on floppy discs to about 20 high school students in 1992. This fall, more than 5,000 studentsaround the world to talk to each other.

More universities are jumping in. After a pilot program this year, Duke, Durham, N.C., is offering an online program this fall in subjects including philosophy and psychology. The University of Washington plans to begin a pilot program next year. Northwestern University, the University of Missouri and University of Iowa report rising enrollment in their online programs.

Taking online classes has become "kind of like earning brass rings to get into college," says Robert C. Vaughn, associate director of the Robinson Center for Young Scholars at the University of Washington, in Seattle. The Robinson center offers on-campus summer programs for gifted students, and next year will offer an online program.

Educational software companies say the gifted-student niche has become one of the fastest growing segments of the "distance learning" market. Apex Learning Inc., Centra Software Inc. and Smarthinking Inc. are selling online course packages, interactive whiteboards and 24-hour online tutoring services to universities with gifted programs.

To help prevent cheating, some companies archive class sessions so universities can review them if they suspect a parent is completing the work. Parents say cheating is unlikely -- students who take online advanced courses are obsessed with excelling. When 11-year-old math whiz Spencer Tofts applied to the University of Delaware's engineering school, the college suggested he improve his writing skills. Spencer took the advice, and aced an online essay-writing course last year at Johns Hopkins. He will be a freshman at Delaware this fall, majoring in electrical engineering and math.

Laura Merciez's 10-year-old son, Joseph, who already is a member of the high-IQ club Mensa, spent hours working on interactive math quizzes in his online class at Johns Hopkins. "It's almost an addiction," says Mrs. Merciez, who lives in Springfield, Va.

Yet these students also benefit in another way: They can meet like-minded people their own age. At his regular school, David says, "nobody really cares about what they're doing." In an online Duke class he took this year, everyone wanted to work, he says.

"Gifted children do not find affiliation with students in their own brick-and-mortar school on a regular basis," says Andrew Mahoney, a Pittsburgh counselor for gifted students who was a child prodigy in art.

Teachers in the online programs say they aren't hindered by the lack of a traditional classroom setting. Lyn Fairchild, who teaches in the online gifted program at Duke, says she can easily meet the needs of students via email.

"When you're teaching face-to-face, you can only talk to one person at a time," she says. "With email, I could cater towards individual needs and I had access to my books and other resources to fully answer questions."