Something's missing at the new Sun Valley Charter High School in Ramona, Calif. There are no textbooks, only computers.

That means students there don't have to lug heavy backpacks -- a familiar ritual for many young Americans who carry books from class to class and home at day's end.

Growing back pain complaints prompted a new California law limiting textbook weight. But some say assignments drawn from the Internet, "e-books" or CD-ROMs will be the real solution.

"It's not the wave of the future; it's the wave of the present," said David Tarr, executive director -- instead of principal -- at Sun Valley High, a public school near San Diego.

Officials there took money normally spent on textbooks and used it for computers. The new school's first students -- about 60 incoming freshmen -- get assignments from such services as Cuestia.com, an online library, and Interactive Mathematics, lessons on computer CD-ROMs.

It sounded nice but unrealistic to Monika Rohall, a 15-year-old Chicagoan. "What about kids who don't have fast-running computers at home?" she asked.

A freshman at Chicago's towering Lane Tech High School, she was stuck navigating four flights of stairs with all her books because she had no time to get to her locker between classes. Back pain from her overloaded pack has caused her to quit the volleyball team.

Such health problems are increasingly common, said Grace Walker, a registered physical therapist in Orange, Calif.

Each year, she and other practitioners say they're seeing more young people with backpack-related pain. In severe cases, it can lead to curvature of the spine.

Some students have found solutions.

Megan Brychcy, a high school senior in Perry, Ga., said a different kind of book bag -- one with a single padded strap intended for one shoulder -- helped her.

Walker's 12-year-old son uses a rolling backpack on wheels. His mom also buys extra textbooks to keep at home.

"Fortunately, I can afford to do that," Walker said. "Most people can't."

That's not an issue at Sun Valley High. Sometimes, students there print out assignments to take home. And if homework requires a computer, they can use the schools' machines after school.

Still, in some lower-income districts, textbooks -- let alone computers -- are scarce.

Elementary students in some Chicago public schools, for example, aren't allowed to take textbooks home out of concern that they will get lost or stolen. Students often copy assignments out of textbooks.

Such funding shortages make CD-ROMs and desktop computers seem unattainable.

"Clearly, electronic delivery will make this problem go away. But I think we're a number of years away from that," said Stephen Driesler, executive director of the school division of the Association of American Publishers.

Still others believe that, with wider use, high-tech devices will become cheaper than costly-to-print textbooks.

That's why, last spring, Richard Bellaver asked his graduate students at Ball State University to test e-books, hand-held devices that present electronic text and pictures. He said the average scores of students who studied only with e-books and those who used traditional textbooks were virtually the same.

Now, he wants to try other high-tech options to see what works best for students -- "and hopefully, save them some money" -- said Bellaver, associate director of the university's Center for Information and Communication Sciences.

Whatever technology becomes dominant, Mark Gross -- chief executive and founder of Data Conversion Laboratory Inc. -- said schools will eventually save money.

"This will be a boon for poor educational districts," said Gross, whose New York-based company has converted into electronic text everything from bulky law books to the Defense Department's weapons systems guides.

Until then, New Jersey is considering imposing a maximum textbook weight. California Gov. Gray Davis (D) signed a similar measure in October.

Textbook publishers, meanwhile, suggest restoring lockers that have been removed at many schools and giving students time between classes to get to them.

Driesler said more students should wear backpacks properly -- on both shoulders instead of one -- even if that method has, as he puts it, a "dweeb factor."

Ninth-grader Sam Taylor uses a PC to work on his algebra lesson during a math class at Sun Valley Charter High School in Ramona, Calif. The school relies on computers for assignments and has eliminated the use of textbooks. That means students there don't have to lug heavy backpacks.Ninth-grader Tim Coles turns to his backpack to look for a CD-ROM containing his literature assignment at a high school in Ramona, Calif. Textbooks no longer used by students rest on a table as ninth-grader Jimmy Maple uses a PC.